JP6692164B2 - Deposition method - Google Patents

Description

  The present invention relates to a film forming method, and more particularly to a film forming object having a metal layer on the surface thereof, and a carbon film formed on the surface of the metal layer by a sputtering method.

  A NAND flash memory is known as a large-capacity nonvolatile semiconductor memory device (see, for example, Patent Document 1). In addition, a film forming method using a sputtering method is used to form a carbon film as an electrode film with high productivity (see, for example, Patent Documents 2 and 3).

  In such a film forming method, a sputtering gas is introduced into the vacuum chamber, power is applied to a carbon target to sputter the target, and the sputtered particles scattered from the target are attached and deposited on the surface of the metal layer. A carbon film is formed. Here, in order to adjust the surface roughness of the thin film to be formed, it is common to apply bias power to the film formation target during sputtering.

  However, it has been found that when a carbon film is continuously formed on a plurality of objects to be processed while the bias power is applied, the film formation rate gradually decreases. Therefore, the inventors of the present invention have conducted extensive research, and sputtered particles from the target collide with the surface of the metal layer to scatter the metal particles, and the metal particles adhere to the surface of the target to react with each other. We came to discover that it was caused by the rise.

JP, 2005-138941, A JP-A-8-31573 International Publication No. 2015/122159

  In view of the above points, the present invention can suppress an increase in cathode voltage and suppress a decrease in film formation rate even when a carbon film is continuously formed on a plurality of processing objects. It is an object of the present invention to provide a film forming method capable of forming the film.

In order to solve the above-mentioned problems, a film formation target has a metal layer composed of a metal having an atomic weight of 90 or more on its surface, and a carbon electrode film is formed on the surface of this metal layer by a sputtering method. The film forming method of the invention comprises a first step of applying a bias power of 0.2 W / cm ² or less to a film forming object to form a first carbon electrode layer on the surface of the metal layer, and a film forming object. characterized in that it comprises a second step of forming a second carbon electrode layer on the surface of 0.2 W / cm ² to have the bias power was introduced more than the first carbon electrode layer. In addition, in the present invention, to apply the bias power of 0.2 W / cm ² or less includes the case where the bias power is set to zero and the bias power is not substantially applied to the film-forming target.

According to the present invention, by setting the bias power applied in the first step to be relatively low, the energy of the metal particles scattered from the surface of the metal layer can be suppressed low, and the metal particles adhere to the target surface. Can be prevented from reacting. Since the surface of the metal layer is covered with the first carbon electrode layer formed in the first step, sputtered particles do not collide with the metal layer even if relatively high bias power is applied in the second step. The metal particles do not adhere to the target surface and react. Therefore, even when a carbon electrode film is continuously formed on a plurality of objects to be processed, it is possible to suppress an increase in cathode voltage and a decrease in film formation rate. Moreover, by forming the second carbon electrode layer with a relatively high bias power, the surface roughness of the carbon electrode film can be adjusted.

In the present invention, it is preferable that the first step has a step of gradually increasing the bias power. According to this, since the bias power is reduced as much as possible until the surface of the metal layer is covered with the first carbon electrode layer, it is possible to further prevent the metal particles from adhering to and reacting with the target surface. Is advantageous.

  In the present invention, by performing the first step for a time period during which the metal layer is covered with the first carbon layer, it may be possible to reliably prevent the metal particles from scattering from the metal layer in the second step.

The present invention is applicable, the metal constituting the metal layer is, Ta, Pt, W, Ru, selected from among Nb and Mo, the carbon electrode film if you deposited by sputtering a pyrocarbon made target Is preferred.

FIG. 3 is a schematic cross-sectional view showing a sputtering apparatus for carrying out the film forming method according to the embodiment of the present invention. Sectional drawing explaining the film-forming method of embodiment of this invention. The figure explaining the film-forming method by the modification of embodiment of this invention. The graph which shows the experimental result which confirms the effect of this invention.

  With reference to FIG. 1, SM is a sputtering apparatus for carrying out the film forming method of the present embodiment. The sputtering apparatus SM includes a vacuum chamber 1 that defines a processing chamber 1a. Below, the ceiling side of the vacuum chamber 1 will be described as "upper" and the bottom side thereof as "lower".

A vacuum pump P including a turbo-molecular pump and a rotary pump is connected to the bottom of the vacuum chamber 1 via an exhaust pipe 10 so that the processing chamber 1a can be evacuated to a predetermined pressure (for example, 10 ⁻⁵ Pa). ing. A gas pipe 12 communicating with a gas source (not shown) and provided with a mass flow controller 11 is connected to the side wall of the vacuum chamber 1, and sputter gas composed of a rare gas such as Ar is supplied into the processing chamber 1a at a predetermined flow rate. It can be introduced.

  A stage 2 is arranged at the bottom of the vacuum chamber 1, an electrostatic chuck (not shown) is provided on the stage 2, and the film formation target W is positioned and held with its metal layer (film formation surface) facing upward. I am trying.

  A target assembly 3 is provided on the ceiling of the vacuum chamber 1. The target assembly 3 is illustrated on the target 31 made of pyrocarbon that is appropriately selected according to the composition of the thin film (carbon film) to be formed, and on the surface (upper surface) facing the sputtering surface 31a of the target 31. The backing plate 32 is made of, for example, Cu and is joined via a bonding material such as indium or tin (omitted). A coolant passage (not shown) is formed in the backing plate 32, and the target 31 can be cooled by circulating the coolant in the coolant passage. The target 31 is connected to an output from a pulse DC power supply having a known structure as the sputtering power supply E1, and a predetermined pulse DC power (for example, 80 kHz to 400 kHz, 1 to 10 kW) is input during sputtering.

  Above the backing plate 32, the magnet unit 4 having a known structure for generating a magnetic field is arranged in the space below the sputtering surface 31a of the target 31, so that the sputtered particles from the target 31 can be efficiently ionized.

  In the processing chamber 1a, cylindrical deposition-preventing plates 5u and 5d are vertically arranged to prevent sputtered particles from adhering to the inner wall surface of the vacuum chamber 1. The drive shaft 51 of the drive means 50 penetrating the bottom plate of the vacuum chamber 1 is connected to the lower deposition preventive plate 5d through a sealing means (not shown). By driving the drive shaft 51, the deposition preventive plate 5d can be moved up and down between the film formation position indicated by a virtual line in the drawing and the transport position indicated by a solid line. The sputtering apparatus SM has a known control means (not shown) including a microcomputer, a sequencer, etc., and controls the operation of the mass flow controller 12, the operation of the vacuum evacuation means P, the operation of the sputtering power supply E1 and the bias power supply E2, and the like. By controlling, a carbon film can be formed on the surface of the film formation target W. Hereinafter, referring also to FIG. 2, in the film forming method of the embodiment of the present invention, the film formation target W has a metal layer M formed of a metal having an atomic weight of 90 or more on the surface of the silicon substrate S, A case where the carbon film C is formed on the surface of the metal layer M by the sputtering method will be described as an example. The metal forming the metal layer M can be selected from Ta, Pt, W, Ru, Nb and Mo.

First, in a state in which the deposition preventive plate 5d is lowered to the transport position, the transport object (not shown) transports the processing target W onto the stage 2 and positions and holds the processing target W with its metal layer facing upward. The attachment plate 5d is raised to the film formation position. When the pressure in the processing chamber 1a reaches a predetermined pressure (for example, 1 × 10 ⁻⁵ Pa), the mass flow controller 12 is controlled to introduce the argon gas at a predetermined flow rate (at this time, the pressure in the processing chamber 1a is reduced). Is within a range of 0.01 to 30 Pa), and pulse DC power is applied from the sputtering power source E1 to the target 31 at 1 kHz to 10 kW at, for example, 80 kHz, and the bias power source E2 causes the stage 2 to have a relatively low level of 0.2 W / cm ² or less. AC power is supplied as bias power to form plasma in the vacuum chamber 1. As a result, the sputter surface 31a of the target 31 is sputtered, and the scattered sputtered particles adhere to and deposit on the surface of the object W to be processed, whereby the first carbon layer C1 is formed on the surface of the metal layer M (first). 1 step). Here, when the sputtered particles collide with the metal layer M exposed at the start of the first step, the metal particles scatter from the metal layer M, but the bias powers applied to the processing target W in the first step are compared. Since it is set to be relatively low, the energy of the metal particles scattered from the metal layer M is low. Therefore, it is possible to prevent the metal particles from adhering to the sputtering surface 31a of the target 31, and even if the metal particles adhere to the sputtering surface 31a, they are easily sputtered, so that the metal particles may react with the sputtering surface 31a. Can be suppressed.

After performing the first step for a predetermined time (for example, the time when the metal layer M is surely covered with the first carbon layer C1), the bias power from the bias power source E2 is set to 0. It is changed to exceed ² W / cm ² (for example, changed to 0.4 W / cm ² ), and the second carbon layer C2 is formed on the surface of the first carbon layer C1 (second step). Although the sputtering power input in the second step is relatively high, the metal layer M is already covered with the first carbon layer C1, so that the sputtered particles do not collide with the metal layer M and the metal particles are targeted. It does not adhere to the sputter surface 31a of 31 and react with it. The time of the second step can be appropriately set according to the thickness of the carbon film C. Further, the upper limit of the bias power applied to the second step can be appropriately set to, for example, 0.7 W / cm ² according to the cooling capacity of the target 31.

  After the film formation of the second carbon layer C2, the introduction of the sputtering gas and the power supply are stopped, the deposition preventive plate 5d is lowered to the transport position, and the processed object W having been film-formed is carried out, and The processing object W is loaded and the above processing is repeated.

  As described above, according to the present embodiment, it is possible to suppress the metal particles scattered from the metal layer M from adhering to and reacting with the sputtering surface 31a of the target 31. Therefore, even when the carbon films C are continuously formed on the plurality of processing objects W, the increase in the cathode voltage can be suppressed and the decrease in the film forming rate can be suppressed. Moreover, by forming the second carbon layer C2 with a relatively high bias power, the surface roughness of the carbon film C can be adjusted within a desired range.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above. In the above-described embodiment, the case where the bias power is set to a predetermined value of 0.2 W / cm ² or less during the first step has been described as an example, but as shown in FIG. 3, the start point (t0) of the first step. Therefore, the bias power may be set to gradually increase. In this case, the first process is performed until time t1 when 0.2 W / cm ² is reached, and the second process is performed after time t1. According to this, since the bias power is reduced as much as possible immediately after the start of the first step, that is, until the surface of the metal layer M is covered with the first carbon layer C1, the metal particles adhere to the target surface and react. This is advantageous because it can be further suppressed.

Next, in order to confirm the above effect, the following experiment was conducted using the above sputtering apparatus SM. In this experiment, as a processing object W, a Ta film as a metal layer M having a thickness of 30 nm was formed on the surface of a Si substrate S having a diameter of 300 mm, and a vacuum having a pyrocarbon target 31 having a diameter of 400 mm assembled therein was used. After setting the processing target W on the stage 2 in the chamber 1, the first carbon layer C1 was formed on the surface of the Ta film M (first step). The film forming conditions of the first step are as follows: Argon gas flow rate: 100 sccm (pressure inside the processing chamber 1a: 0.2 Pa), input power to the target 31: 80 kHz, 2 kW, bias power: 0 W, target 31 and target object W. Distance (distance between TSs): 190 mm, film formation time: 30 sec. After the completion of the first step, the second carbon layer C2 was formed under the same conditions as the first step except that the bias power was increased to 0.4 W / cm ² (second step). FIG. 4 shows the results of measuring the cathode voltage and the film formation rate in the second step of the first to fifth sheets by continuously forming such a carbon film C on the five processing objects W. Show. According to this, it was confirmed that the cathode voltage (average value) was stable at about 514 V and the film formation rate was stable at about 15 Å / min. It was also confirmed that the surface roughness of the formed carbon film C can be adjusted within a desired range.

Further, 0.01 W ^/ cm ² the bias power of the first ^{step, 0.07W / cm 2, 0.1W /} cm 2, except for changing the 0.2 W / cm ^2, it was deposited with the experimental conditions When the cathode voltage and the film formation rate were measured in each case, the same results as in the above experiment were obtained. Further, when the Pt film, the W film, the Ru film, the Nb film, and the Mo film made of a relatively heavy metal having an atomic weight of 90 or more is used as the metal layer M instead of the Ta film, the same result as the above experiment is obtained. Was given. This is because, in the case of a metal having an atomic weight of 90 or more, when the sputtered particles or argon ions collide with the metal layer M, the ratio of scattering in the vertical direction from the processing target W is large, and the amount reaching the sputtering surface 31a of the target 31 is large. This is probably because there are many.

  For comparison with the above experiment, the following comparative experiment was performed. In the comparative experiment, the first step was not performed (that is, the first carbon layer C1 was not formed), and only the second step was performed. Also in this case, the cathode voltage and the film formation rate during the film formation of the first to fifth films were measured, and the measurement results are also shown in FIG. 4 as a comparative example. According to this, it was confirmed that the cathode voltage increased after the second sheet and the film formation rate decreased after the third sheet.

Further, an experiment was conducted under the same conditions as the comparative experiment except that the bias power was changed to 0.3 W / cm ² and 0.4 W / cm ² , and the same result as the comparative experiment was obtained. From this, when the bias power is set to 0.3 W / cm ² , the metal particles scattered from the metal layer M adhere to the sputter surface 31a and react with each other. It has been found that the power needs to be set to 0.2 W / cm ² or less. An experiment was conducted under the same conditions as the comparative experiment except that the object W to be treated was a silicon substrate, but the same results as the above-described invention experiment were obtained. That is, no increase in cathode voltage or decrease in film formation rate was confirmed even without performing the first step. From this, it was found that the increase in the cathode voltage was caused by the reaction of the metal particles from the metal layer M on the sputtering surface 31a.

According to the above experiment, if the second step of setting the bias power to exceed 0.2 W / cm ² is performed after performing the first step of setting the bias power to 0.2 W / cm ² or less, It has been found that it is possible to prevent the increase, and thus to suppress the decrease in the film forming rate.

  W ... Object to be treated, M ... Ta layer (metal layer), C ... Carbon film, C1 ... First carbon layer, C2 ... Second carbon layer.

Claims (4)

A film forming method in which a film forming object has a metal layer composed of a metal having an atomic weight of 90 or more on the surface thereof, and a carbon electrode film is formed on the surface of the metal layer by a sputtering method,
A first step of applying a bias power of 0.2 W / cm ² or less to a film formation object to form a first carbon electrode layer on the surface of the metal layer;
Deposition, wherein a bias power of more than 0.2 W / cm ² in film formation object was charged and a second step of forming a second carbon electrode layer on a surface of the first carbon electrode layer Method.   The film forming method according to claim 1, wherein the first step includes a step of gradually increasing the bias power. The film forming method according to claim 1, wherein the first step is performed for a time period during which the metal layer is covered with the first carbon electrode layer. Wherein the metal, Ta, Pt, W, is selected from among Ru, Nb and Mo, the carbon electrode film any of claims 1 to 3, wherein the film formation to isosamples sputtering pyrocarbon made target The film forming method as described in 1 above.

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