JP2021147678A - Formation method of dielectric film - Google Patents

Abstract

To provide a formation method of a dielectric film capable of forming a dielectric film and suppressing a secular change of a warpage of a substrate to be treated as much as possible when the dielectric film is deposited on the other surface of the substrate to be treated.SOLUTION: A formation method of a dielectric film for forming the dielectric film on the other surface Swb of a substrate Sw to be treated, assuming that a predetermined thin film is deposited on one surface Swa of the substrate Sw to be treated, includes a film deposition step where the substrate to be treated and a target 2 are arranged in a vacuum chamber 1, an inert gas is introduced to the vacuum chamber in a vacuum atmosphere, and the dielectric film is deposited on the other surface of the substrate to be treated by sputtering the target, and further includes an annealing step where the substrate to be treated is heated to a predetermined temperature within a predetermined time Ts after the end of the film deposition step.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for forming a dielectric film in which a predetermined thin film is formed on one surface of a substrate to be processed and a dielectric film is formed on the other surface of the substrate to be processed.

In the manufacturing process of a semiconductor device, there is a step of performing a film forming process on one surface of a substrate to be processed (hereinafter referred to as “substrate”) such as a silicon wafer. In recent years, there has been a tendency for the substrate to have a large diameter and a thin wall, and such a substrate usually has a warp. Then, when a predetermined thin film is formed on one surface of the substrate (that is, the surface forming the device structure) by, for example, a film forming process by a sputtering method, the stress of the formed thin film increases the warp (plurality). When thin films are laminated, the warp becomes even larger). In order to reduce the warpage of the substrate as much as possible, a predetermined thin film is formed on one surface of the substrate, and then a dielectric film such as a silicon nitride film is formed on the other surface of the substrate. (For example, see Patent Document 1).

However, it was found that even if a dielectric film was formed on the other surface of the substrate, the warp of the substrate changed with time (that is, it returned to the state before the dielectric film was formed). Therefore, the present inventors have conducted extensive research and have come to find that the stress of the formed dielectric film decreases with the passage of time, and that the warp of the substrate changes with time due to this. .. This is because when the dielectric film is formed, a rare gas (for example, argon gas) introduced into the vacuum chamber is taken into the dielectric film, and a rare gas atom (for example, argon) remaining in the dielectric film is taken into the dielectric film. It was thought that the atom) causes a decrease in stress over time.

Japanese Unexamined Patent Publication No. 2009-295889

The present invention has been made based on the above findings, and when a dielectric film is formed on the other surface of the substrate to be treated, it is possible to suppress the change in warpage of the substrate to be treated with time as much as possible. An object of the present invention is to provide a method for forming a dielectric film capable of forming a dielectric film.

In order to solve the above problems, it is assumed that a predetermined thin film is formed on one surface of the substrate to be processed, and a dielectric film of the present invention is formed on the other surface of the substrate to be processed. The method is to place the substrate to be processed and the target in a vacuum chamber, introduce a rare gas into the vacuum chamber in a vacuum atmosphere, and sputter the target to form a dielectric film on the other surface of the substrate to be processed. It is characterized by further including an annealing step of heating the substrate to be processed to a predetermined temperature within a predetermined time from the end of the film forming step.

According to the present invention, by adding an annealing step and removing the noble gas atom (argon atom) unavoidably incorporated into the dielectric film in the previous step (deposition step), the time elapses. The accompanying decrease in stress of the dielectric film can be suppressed as much as possible, and as a result, the change in warpage of the substrate with time can be suppressed as much as possible. If the annealing step is not performed within a predetermined time (within 24 hours) after the film formation step is completed, the stress decrease of the dielectric film with the passage of time cannot be suppressed as much as possible, and the dielectric film cannot be suppressed. It was confirmed that when the silicon nitride film was formed as a film, the stress of the dielectric film was rather reduced when the annealing step was carried out at a temperature lower than 750 ° C. According to the present invention, in the film forming step, a rare gas and a nitrogen-containing gas are introduced into a vacuum chamber in a vacuum atmosphere, and reactive sputtering is performed in a transition region to form a silicon nitride film having tensile stress. It is preferable to apply it when

The figure schematically explaining the sputtering apparatus which carries out the method of forming the dielectric film of embodiment of this invention. The figure schematically explaining the film formation chamber shown in FIG. The plan view of the annular member of the substrate stage shown in FIG. The graph which shows the experimental result which confirms the effect of this invention. The graph which shows the experimental result which confirms the effect of this invention.

Hereinafter, referring to the drawings, the substrate to be processed is a silicon wafer in which a thin film is formed on one surface Swa (hereinafter referred to as “substrate Sw”), and nitrided as a dielectric film on the other surface Swb of the substrate Sw. An embodiment of the method for forming a dielectric film of the present invention will be described by taking the case of forming a silicon film as an example.

With reference to FIG. 1, the SM is a sputtering apparatus composed of a cluster tool that implements the method for forming a dielectric film of the present embodiment. The sputtering apparatus SM includes a transport chamber Tc in which the transport robot R is arranged, a film forming chamber Pc1 arranged so as to surround the transport chamber Tc, an annealing chamber Pc2, and a load lock chamber Lc. Exhaust pipes leading to a vacuum pump unit (may be omitted) are connected to each of the transport chamber Tc, the load lock chamber Lc, the film forming chamber Pc1 and the annealing chamber Pc2, so that each chamber can be evacuated. ing. Further, a vent gas line (not shown) is further connected to the load lock chamber Lc so that the load lock chamber Lc can be vented to atmospheric pressure. As the transfer robot R, for example, a known so-called frog leg type having a robot arm 10a and a robot hand 10b provided at the tip of the robot arm 10a and holding the substrate Sw can be used, and this transfer robot R can be used. The robot R can convey the substrate Sw to a predetermined position in each room. Further, the transport chamber Tc, the load lock chamber Lc, the film forming chamber Pc1 and the annealing chamber Pc2 are connected to each other via a partition valve Iv so that the chambers can be isolated from each other.

With reference to FIG. 2, the film forming chamber Pc1 is defined by the vacuum chamber 1. An exhaust pipe 11 leading to a vacuum pump unit Pu including a turbo molecular pump, a rotary pump, or the like is connected to the vacuum chamber 1 so that the film forming chamber Pc1 can be evacuated. A gas pipe 13 provided with a mass flow controller 12 is connected to the side wall of the vacuum chamber 1, and a rare gas (for example, argon gas) and, if necessary, a nitrogen gas can be introduced into the film forming chamber Pc1 at predetermined flow rates, respectively. It has become like. In the following, terms indicating directions such as "up" and "down" will be described with reference to the installation posture shown in FIG.

A silicon target 2 is provided on the upper side wall of the vacuum chamber 1 via an insulator Io1 in a state of being joined to the backing plate 21. An output from a high-frequency power source as a sputtering power source Ps is connected to the target 2, so that high-frequency power of a predetermined frequency can be applied to the target 2 during sputtering. On the inner surface of the lower wall of the vacuum chamber 1, a substrate stage St is arranged via an insulator Io2 so as to face the target 2.

The substrate stage St is arranged on a metal base 3 having a contour slightly larger than that of the substrate Sw and on the upper surface of the base 3, and one surface (lower surface) Swa of the substrate Sw is in contact with the upper surface of the base 3. An annular member 4 that supports the substrate Sw so as not to be provided (so that the gap d exists) is provided. A refrigerant passage 3a is bored in the base 3, and the base 3 can be cooled to a predetermined temperature (for example, -20 to 30 ° C.) by circulating a refrigerant supplied from a chiller (not shown). With reference to FIG. 3, a protrusion 31 is formed in the center of the upper surface of the base 3, and the lower portion of the inner peripheral surface of the annular member 4 is brought into contact with the outer peripheral surface of the protrusion 31 on the base 3. The annular member 4 is positioned. The annular member 4 includes an annular wall 41 and a flange portion 42 that extends outward from the outer peripheral surface of the annular wall 41 and covers a part of the upper surface of the base 3. The annular wall 41 is composed of a fixed wall portion 41a and two movable wall portions 41b having a predetermined arc length, and the outer edge portion of the substrate Sw is in contact with the inclined surface 41c forming the upper part of the inner peripheral surface thereof. The substrate Sw can be supported by contacting the substrate Sw. The outer edge of the substrate Sw is a region where the device structure is not formed, for example, a region within 2 mm from the outer edge of the substrate Sw. The two movable wall portions 41b are connected by a connecting member 43, and a drive shaft 44a of an actuator 44 provided so as to penetrate the central portion of the base 3 in the vertical direction is connected to the center of the lower surface of the connecting member 43. By moving the drive shaft 44a up and down by the actuator 44, the movable wall portion 41b can move up and down with respect to the fixed wall portion 41a, whereby the substrate Sw is moved in a direction close to and separated from the upper surface of the base 3. It is movable.

Further, the annealing chamber Pc2 is defined by another vacuum chamber 1a. The annealing chamber Pc2 is also provided with the substrate stage St so that the substrate Sw can be supported so that the lower surface Swa of the substrate Sw does not come into contact with the upper surface of the base 3. A lamp unit Lu is arranged above the annealing chamber Pc2 so that the substrate Sw supported by the substrate stage St can be heated to a predetermined temperature (for example, a temperature of 750 ° C. or higher). As the lamp unit Lu, a known lamp unit including, for example, an infrared lamp can be used, and therefore detailed description thereof will be omitted.

The sputtering apparatus SM has a control means C equipped with a microcomputer, a sequencer, and the like, and operates a transfer robot R, a partition valve Iv, a vacuum pump unit Pu, an actuator 44, and a mass flow controller 12. , The operation of the sputter power supply Ps, the operation of the lamp unit Lu, etc. are controlled in an integrated manner. Hereinafter, a method for forming a dielectric film will be described by taking as an example a case where a silicon nitride film is formed on the other surface (upper surface) Swb of the substrate Sw by using the sputtering apparatus SM.

When the substrate Sw before film formation is put into the load lock chamber Lc with the other side Swb facing upward and the load lock chamber Lc is evacuated to a predetermined degree of vacuum, the substrate Sw is load-locked by the transfer robot R. It is transported from the chamber Lc to the transport chamber Tc. At the same time, when the inside of the vacuum chamber 1 (deposition chamber Pc1) is evacuated to a predetermined degree of vacuum (for example, 1 × 10 ^-5 Pa), the actuator 44 moves the movable wall portion 41b up to a predetermined height position. In this state, the substrate Sw held by the robot hand 10b of the transfer robot R is delivered to the movable wall portion 41b. When the robot hand 10b is retracted, the substrate Sw is supported by a part of its outer edge portion abutting on the inclined surface 41c of the movable wall portion 41b. Then, when the movable wall portion 41b is moved downward by the actuator 44, the remaining portion of the outer edge portion of the substrate Sw comes into contact with the inclined surface 41c of the fixed wall portion 41a, so that a gap d is left from the upper surface of the base 3 and the substrate is formed. Sw is supported by an annular wall 41 all around it. After that, argon gas and nitrogen gas were introduced as sputtering gases at a flow rate of 70 to 80 sccm and 15 to 35 sccm, respectively (at this time, the pressure in the film forming chamber Pc1 was 0.1 to 0.4 Pa), so-called reactive sputtering. It is retained in the transition region (the region that transitions from the metal mode to the compound mode). At the same time, 4 kW to 6 kW of high frequency power of, for example, 150 KHz to 13.56 MHz is input to the target 2 from the high frequency power supply Ps. As a result, a plasma atmosphere is formed in the vacuum chamber 1, and the target 2 is reactively sputtered. During sputtering, the upper surface of the base 3 is cooled to a predetermined temperature (22 ° C.) by circulating the refrigerant through the refrigerant passage 3a of the base 3. A silicon nitride film is formed on the surface of the substrate Sw by adhering and depositing the reaction product of the sputtered particles scattered from the target 2 by sputtering and the nitrogen gas on the surface of the substrate Sw (film formation step). When the film forming process is performed for a predetermined time, the film-deposited substrate Sw is taken out from the film-forming chamber Pc1 to the transport chamber Tc by the transfer robot R.

A rare gas (for example, argon gas) introduced as a sputter gas is inevitably taken into the film of the silicon nitride film formed in this way, and the argon atom remaining in the silicon nitride film is with the passage of time. It causes a decrease in stress, which causes the warp of the substrate Sw to change over time.

Therefore, in the present embodiment, the substrate Sw is conveyed in-situ from the film forming chamber Pc1 to the annealing chamber Pc2 within a predetermined time Ts from the end of the film forming process, and is exposed to the vacuum atmosphere following the film forming process. The substrate Sw of the above is heated to a predetermined temperature by the lamp unit Lu (annealing step). Here, the time from the end of the film forming step to the annealing step is set to a time (for example, within 24 hours) in which the stress decrease of the silicon nitride film with the passage of time can be suppressed. Further, the temperature of the substrate Sw heated in the annealing step is set to a temperature (for example, 750 ° C. or higher) at which argon atoms incorporated in the silicon nitride film can be efficiently removed. After the annealing treatment is performed for a predetermined time (for example, 40 to 70 seconds), the lamp unit Lu is temporarily stopped to cool the substrate Sw. When the substrate Sw is cooled to a predetermined temperature (for example, 200 ° C.), the substrate Sw is taken out from the annealing chamber Pc2 and conveyed to the load lock chamber Lc, the load lock chamber Lc is vented to atmospheric pressure, and then the substrate Sw is recovered. ..

According to the present embodiment described above, nitriding with the passage of time is performed by adding an annealing step and removing argon atoms inevitably incorporated into the silicon nitride film in the film forming step which is the previous step. The decrease in stress of the silicon film can be suppressed as much as possible, and as a result, the change in warpage of the substrate Sw with time can be suppressed as much as possible.

Next, in order to confirm the above effect, the following experiment was carried out using the above sputtering apparatus SM. In the invention experiment, a bare silicon wafer having a diameter of 300 mm was used as the substrate Sw, and the warp of the substrate Sw (the height of the center of the substrate Sw from the reference plane without adsorbing the substrate Sw) was measured by a known BOW. It was +50 μm (ie, the center of the substrate Sw was about 50 μm higher than the extension). This substrate Sw is supported by the stage St of the film forming chamber Pc1 (the gap d between the upper surface of the base 3 and the substrate Sw at this time is 0.5 mm), and the argon gas is evacuated at a flow rate of 75 sccm and the nitrogen gas is evacuated at a flow rate of 30 sccm. Each of them is introduced into the chamber 1 (the pressure in the vacuum chamber 1 at this time is about 0.4 Pa), and at the same time, 6 kW of high frequency power of 150 kHz is applied to the silicon target 2 from the high frequency power supply Ps to make the target. 2 was sputtered to form a silicon nitride film on the upper surface of the substrate Sw with a film thickness of 110 nm (deposition step). During the film formation, the upper surface of the base 3 was cooled to 22 ° C. As shown in FIG. 5, the stress of the silicon nitride film immediately after the film formation process (tensile stress in this experiment) was measured by a known optical lever type stress measuring device, for example, and found to be 266 MPa, and the warpage of the substrate Sw. Was measured by the above measuring method (BOW) and found to be -17.15 μm (that is, the outer extension of the substrate Sw was 17.15 μm higher than the center). After the measurement, the substrate Sw was conveyed to the annealing chamber Pc2, and two hours after the completion of the film forming process, the substrate Sw was heated to a temperature of 750 ° C. by the lamp unit Lu in the annealing chamber Pc2 in a vacuum atmosphere to perform the annealing treatment. (Annealing process). After the annealing treatment was carried out for 40 seconds, the lamp unit Lu was temporarily stopped to cool the substrate Sw. When the substrate Sw was cooled to 200 ° C., the substrate Sw was taken out from the annealing chamber Pc2. The stress of the silicon nitride film immediately after the completion of the annealing step was measured and found to be 385 MPa, and it was confirmed that the stress of the silicon nitride film was increased by 119 MPa by performing the annealing treatment. Moreover, when the warp of the substrate Sw immediately after the completion of the annealing step was measured, it was -25.02 μm. Next, when the stress of the silicon nitride film was measured 24 hours and 72 hours after the completion of the film forming process, both were 378 MPa, which was equivalent to that immediately after the completion of the annealing process (1.2% decrease). confirmed. Further, when the warpage of the substrate Sw 24 hours and 72 hours after the completion of the film forming process was determined, it was confirmed that the values were -24.71 μm and -24.78 μm, which were equivalent to those immediately after the completion of the annealing process. .. By carrying out the annealing step within Ts for a predetermined time from the end of the film forming step in this way, the stress decrease of the silicon nitride film with the passage of time is suppressed as much as possible, and as a result, the warp of the substrate Sw changes with time. It was found that can be suppressed as much as possible.

Next, in Comparative Experiment 1, a film forming step was carried out in the same manner as in the above-mentioned invention experiment, except that the annealing step was not carried out. The stress of the silicon nitride film immediately after the film formation step was measured and found to be 267 MPa, and the warpage of the substrate Sw was measured by the above measuring method (BOW) and found to be -17.55 μm (see FIG. 5). .. When the stress of the silicon nitride film was measured 24 hours and 72 hours after the completion of the film forming process, the stresses were 240 MPa and 232 MPa, respectively, and it was confirmed that the stress decreased by 10% or more immediately after the completion of the film forming process. Further, when the warpage of the substrate Sw 24 hours and 72 hours after the completion of the film forming process was determined, it was -15.76 μm and -15.29 μm, respectively, and the warp of the substrate Sw changed significantly immediately after the completion of the film forming process. It was confirmed that As described above, it was found that when the annealing step was not performed, the stress of the formed silicon nitride film decreased with the passage of time, and the warp of the substrate Sw changed with time due to this.

Next, in the comparative experiment 2, the conditions are the same as those of the above-mentioned invention experiment except that the film forming step is performed for 1310 seconds and then the annealing step is performed 24 hours or more (for example, 72 hours) after the film forming step is completed. The film forming step and the annealing step were carried out in. According to this comparative experiment 2, although not shown in particular, it was confirmed that the stress decrease of the silicon nitride film with the passage of time could not be suppressed as much as possible. Further, when the warp of the substrate Sw was measured, it was -311.28 μm immediately after the end of the film forming process, -281.51 μm 72 hours after the end of the film forming process (before the annealing process), and -257 in the annealing process. It was .49 μm. As described above, even if the annealing step is performed after a lapse of a predetermined time from the end of the film forming step, the stress decrease of the silicon nitride film with the lapse of time cannot be suppressed as much as possible, and the warp of the substrate Sw is also caused. It was found that it changed over time.

Next, in Comparative Experiment 3, the film forming step and the annealing step were carried out under the same conditions as the above-mentioned invention experiment except that the film forming step was performed for 1200 seconds and the annealing temperature was set to 500 ° C. .. According to this comparative experiment 3, although not shown in particular, it was confirmed that the stress decrease of the silicon nitride film with the passage of time could not be suppressed as much as possible. Further, when the warp of the substrate Sw was measured, it was -347.85 μm immediately after the completion of the annealing step, -333.50 μm 24 hours after the end of the film formation step, and -329.77 μm 48 hours later. In this way, even if the annealing step is carried out within a predetermined time from the end of the film forming step, if the annealing step is carried out at a temperature lower than 750 ° C., the stress of the silicon nitride film is rather lowered, and the stress of the silicon nitride film is reduced accordingly. It was found that the warp changed over time.

Although the embodiments of the present invention have been described above, various modifications are possible as long as they do not deviate from the scope of the technical idea of the present invention. In the above embodiment, the case where the silicon nitride film is formed as the dielectric film has been described as an example, but the dielectric film is not limited to this, and a dielectric film containing nitrogen and silicon such as a silicon oxynitride film is used. The present invention can also be applied when forming. In the same way as the silicon nitride film, the stress of the formed dielectric film decreases with the passage of time in these dielectric films containing nitrogen and silicon, and as a result, the warp of the substrate over time. I confirmed that it would change. Further, in the above embodiment, a case where a silicon nitride film is used as the target 2 and a silicon nitride film is formed by reactive sputtering is described as an example, but the silicon nitride target 2 is sputtered to form silicon nitride. It can also be applied when forming a film.

Further, in the above embodiment, the substrate Sw is conveyed in-situ from the film forming chamber Pc1 to the annealing chamber Pc2, and the substrate Sw in a state of being exposed to the vacuum atmosphere is heated to a predetermined temperature following the film forming process to anneal. The case where the step is performed has been described as an example, but the present invention is not limited to this, and the case where the substrate Sw is once exposed to the air atmosphere after the film forming step and then the annealing step is performed (for example, the film forming step and the annealing step are different). The present invention can also be applied to the case where it is carried out by an apparatus). In this case, it is preferable to carry out the annealing step in a vacuum atmosphere.

St ... A predetermined time from the end of the film forming process, Sw ... Substrate (processed substrate), Swa ... One surface of the substrate, Swb ... The other surface of the substrate, 1 ... Vacuum chamber, 2 ... Target.

Claims (3)

In a method for forming a dielectric film in which a predetermined thin film is formed on one surface of a substrate to be processed and a dielectric film is formed on the other surface of the substrate to be processed.
A film formation in which a substrate to be processed and a target are arranged in a vacuum chamber, a rare gas is introduced into the vacuum chamber in a vacuum atmosphere, and the target is sputtered to form a dielectric film on the other surface of the substrate to be processed. Including the process
A method for forming a dielectric film, which further comprises an annealing step of heating a substrate to be processed to a predetermined temperature within a predetermined time from the end of the film forming step. The method for forming a dielectric film according to claim 1, wherein a silicon nitride film is formed as the dielectric film.
The annealing step is a method for forming a dielectric film, which comprises heating a substrate to be treated to a temperature reaching 750 ° C. In the method for forming a dielectric film according to claim 2,
In the film forming step, a rare gas and a nitrogen-containing gas are introduced into a vacuum chamber in a vacuum atmosphere, and a silicon nitride film having a tensile stress is formed by reactive sputtering in a transition region. A method for forming a dielectric film.

Images