JPS6127462B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for forming a reactant film using a reactive sputtering method. A reactive gas such as oxygen, nitrogen, methane, or hydrogen sulfide is mixed into an inert gas that causes a discharge using a single substance as a target, and sputtering is performed to form oxides or nitrides of the target substance on a substrate facing the target. In reactive sputtering technology, which forms reaction products such as carbides, sulfides, etc., the target is covered with an atmosphere with a low concentration of reactive gas, increasing the concentration of the reactive gas near the substrate, and separating the reactive gas and inert gas. A reactive sputtering device has been proposed that separates . This is because in the conventional parallel plate bipolar sputtering method, the reactive gas comes into contact with the target, so it first reacts on the target and the reaction product is sputtered, so the film formation rate is generally slow. On the other hand, when trying to form reactants of the target material on the substrate by applying large sputtering power to prevent reactions on the target, it is difficult to control the degree of reaction of the film, making it difficult to form intermediate reactants. There was a drawback. The device proposed to address these shortcomings is
The target is surrounded by a shield plate in a vacuum chamber and separated into a shield chamber, an inert gas is introduced into the shield chamber, and a reactive gas is introduced near the substrate. However, the shield plate naturally has a window that allows particles spattered from the target to pass through.
Because the conductance of this window is large and the shielded chamber does not have an exhaust system, it is almost impossible to separate the inert gas and the reactive gas. Further, the sputtered particles widely adhere to the wall surface of the vacuum chamber, and the resulting getter action effectively reduces the reactive gas partial pressure to a very low level, which is problematic in terms of reactivity control. Furthermore, since the substrate is directly exposed to plasma, the substrate temperature increases, making it difficult to control the substrate temperature, and causing damage to the formed film due to ion collisions. SUMMARY OF THE INVENTION An object of the present invention is to provide a reactive sputtering apparatus that eliminates the above-mentioned drawbacks of the prior art, can control reactive gas pressure in the vicinity of a substrate over a wide range, and can suppress an increase in substrate temperature. A feature of the present invention is that a partition wall having a large number of small holes of appropriate length is provided between a target and a substrate provided opposite to the target, and a vacuum chamber is connected to a discharge chamber on the target side and a substrate side. The discharge chamber is connected to an inert gas introduction device, the thin film formation chamber is connected to a reactive gas introduction device, and each chamber is connected to an exhaust device. , the inert gas and the reactive gas can be easily separated in the two chambers, and reactions on the target can be prevented. Another feature of the present invention is that since the discharge occurs only between the target and the above-mentioned barrier ribs, the substrate is not directly exposed to plasma and the temperature of the substrate is less likely to rise. Another feature of the present invention is that the influence of getter action on the reactive gas partial pressure is reduced. Another feature of the present invention is that since the partition wall has a large number of small holes, it is easy to make the film thickness distribution uniform. The present invention will be explained below with reference to Examples. Example 1 The configuration of this example is shown in FIGS. 1 and 2. FIG. 1 is an overall configuration diagram of the device, and FIG. 2 shows an example of the arrangement of small holes formed in the partition wall. In Figure 1,
1 is a vacuum chamber, 2 is a target, and 3 is a target support, and the vacuum chamber 1 and the target support 3 are electrically insulated. 4 is a substrate on which a thin film is to be formed, 5 is a substrate support, and a substrate rotation device 13 is attached to the substrate in order to make the thin film uniform.
The vacuum chamber 1 is divided into two chambers, a discharge chamber on the target 2 side and a thin film forming chamber on the substrate 4 side, by a partition wall 11 having a large number of small holes of appropriate length. The discharge chamber is equipped with an inert gas introduction device 6 such as argon, and the thin film formation chamber is equipped with a reactive gas introduction device 7 such as oxygen and nitrogen, and exhaust devices 8 and 9 are installed in each chamber.
is installed. 10 is a DC or high frequency power source in the discharge chamber, and 12 is a target 2 by discharge.
The flight path of the particles sputtered from the partition wall 11 and passing through the small holes in the partition wall 11 is shown. FIG. 2 conceptually shows an example of the arrangement of a small hole 111 made in a partition wall 11 in combination with the substrate rotation 13 to make the film thickness uniform. They are evenly spaced on the section. The origin of the spiral is aligned with the center of substrate rotation. Next, the operation of each part will be explained. First, it will be shown that in this example, the concentrations of the inert gas and the reactive gas can be significantly different between the discharge chamber and the thin film formation chamber. Partition wall 11
The conductance of the opening is C (/sec), and the inert gas flow rate from the inert gas introducing device 6 is Q _A
(Torr・/sec), the reactive gas flow rate from the reactive gas introduction device 7 is Q _B (Torr・/sec), and the exhaust speeds by the exhaust devices 8 and 9 are S ₁ and S ₂ (/sec), respectively.
sec), the inert gas partial pressure P ^A ₁ (Torr) in the discharge chamber, the reactive gas partial pressure P ^B ₁ (Torr), and the inert gas partial pressure P ^A ₂ in the thin film forming chamber.
(Torr) and reactive gas partial pressure P ^B ₂ (Torr) are given by equations (1) to (4), respectively, if the interaction between the inert gas and the reactive gas is ignored. P ^A ₁ =(S ₂ +C)Q _A /S ₁ S ₂ +(S ₁ +S ₂
)C……(1) P ^B ₁ =CQ _B /S ₁ S ₂ +(S ₁ +S ₂ )C……(2
) P ^A ₂ = CQ _A /S ₁ S ₂ + (S ₁ + S ₂ ) C……(3
) P ^B ₂ = (S ₁ + C) Q _B /S ₁ S ₂ + (S ₁ + S ₂
)C...(4) From these formulas, P ^A ₁ /P ^B ₁ = (S ₂ +C)Q _A /
CQ _B , P ^B ₂ /P ^A ₂ (S ₁ +C) Q _B /CQ _A. As you can see, in both chambers, inert gas,
In order to separate the reactive gas, it is necessary to increase the pumping speeds S ₁ and S ₂ of both chambers or to decrease the conductance C of the partition opening. However, when the pumping speeds S ₁ and S ₂ are increased, the gas flow rates Q _A and Q _B must be made extremely large in order to obtain a gas pressure of around 10 ^-2 (Torr) during normal sputtering. Therefore, it is more appropriate to reduce the conductance C of the partition opening. If the diameter of the small hole made in the partition wall 11 as in this example is D and the length is, the conductance will be 1/(3/4D+1) compared to the case of a small hole with no length, for example /D= When set to 10, the conductance drops to 1/8.5. In order to effectively utilize the reduction in conductance due to small holes having such a length and to minimize the decrease in film formation rate, 1/D20 is preferable. In addition, the opening angle of the sputter particles in the flight direction is set to 45° (=
It can be controlled within tan ^-1 (D/)). In this example, approximately 2000 holes of =20 (mm) and D = 2 (mm) are opened (total opening area = 63 cm ² ),
Its conductance C=85 (/sec).
Using such a partition, the pumping speed S ₁ = S ₂ = 500
(/sec), Q _A = 4.7 (Torr・/sec) (= 380 c.c./min in standard condition), _{Q B} = 2.35
(Torr・/sec) (=190c.c./min), and when argon gas is used as the inert gas and oxygen gas is used as the reactive gas, the concentrations of argon gas and oxygen gas are both equal as shown in the table below. It makes a big difference in the room.

[Table] Using the apparatus of this example, the reactive gas partial pressure and the inert gas partial pressure in both chambers can be controlled almost independently, and the degree of reaction can be easily controlled. Furthermore, when the apparatus of this example is used as a normal sputtering apparatus with the supply of reactive gas stopped, the residual impurity gas in the thin film forming chamber can be kept low and a high quality film can be obtained. Sputtering of the target 2 is caused by a discharge high frequency power source 10 connected between the target 2 and the partition wall 11 or the vacuum chamber 1 which is electrically connected thereto. If target 2 is a good conductor, power supply 10
may be a DC power supply. At this time, discharge occurs between the target 2 and the partition wall 11, and the particles sputtered from the target pass through the small holes in the partition wall 11 as indicated by arrow 12 and reach the substrate. Spatter particles react with reactive gases while in flight or on the substrate. At this time, the substrate is not directly exposed to plasma, the rise in substrate temperature can be kept low, and the formed film is less likely to be damaged by ion bombardment. Further, as can be seen from the arrow 12, the partition wall 11
Since the small holes 111 formed in the sputtered particles have a certain length, the spatter particles have unidirectionality. this is,
This is advantageous in controlling the orientation of films such as magnetic thin films. Furthermore, in this example, most of the spatter particles adhere to the wall surface of the discharge chamber, so even if the spatter particles have a strong getter effect on the reactive gas, the partial pressure of the reactive gas in the thin film forming chamber will increase. The impact on this is extremely small. If this is shown in accordance with the example in which the numerical value is increased in this example, it will be as follows. If aluminum, iron, etc., which have a strong getter effect on oxygen, adhere to the inside of the vacuum chamber, the pumping speed for oxygen will reach approximately 10 ⁴ (/sec). Therefore, if we set S ₁ = 10 ⁴ (/sec) in equation (4) and leave the other values as before, the oxygen partial pressure in the thin film formation chamber will be 4.0 × 10 ^-3 (Torr), which will not change at all. Recognize. In this way, the device of this example consumes extremely little reactive gas due to getter action.
It can be seen that the reactive gas is effectively used in the reaction of the film deposited on the substrate. Next, a description will be given of how to make the film thickness distribution uniform when using a partition wall having the arrangement of small holes shown in FIG. The sputtered particles that have passed through one small hole form a band-shaped film on the substrate due to the rotation of the substrate, with the maximum film thickness near the center radius. In order to make the distribution uniform near the radius of this band, it is sufficient to overlap the contributions from small holes with slightly different substrate rotation radii. Furthermore, in order to make the film thickness distribution in the direction of the rotation radius of the substrate uniform, it is sufficient to superimpose the contributions of the small holes in the number proportional to the rotation radius of the substrate. An example of such a small hole arrangement is the second hole arrangement.
An example of this is to arrange them at equal intervals on a spiral represented by γ=Aθ in polar coordinates as shown in the figure. In this example, spiral 1 with A=2 (mm/rad)
Small holes 111 (diameter 2 mm) were arranged at equal intervals of 4 mm between centers on the solid line portion of 12, and the distribution in the radial direction of the substrate support at this time was very uniform as shown by the solid line in Fig. 3. It is. The dotted line in FIG. 3 shows the film thickness distribution when the small holes 111 are opened at the same intervals on the inside and outside of the spiral line 112. As can be seen from this dotted line, the film thickness distribution cannot be made uniform at the center of substrate rotation. Therefore, this example is suitable for cases such as magnetic disks where there is no need to form a film at the center of rotation of the substrate. When Fe ₃ O ₄ or α-Fe ₂ O ₃ is formed using the partition wall of this example with iron as the target, argon gas as the inert gas, and oxygen as the reactive gas, the film formation rate is approximately 0.05 Å. /min, which is very small. Use a magnetron type target as a target,
If the size and arrangement of the holes are made appropriate, the film formation rate can be improved by more than one order of magnitude. Example 2 The schematic structure of this example is shown in FIGS. 4 and 5. FIG. 4 is a schematic diagram of the sputtering apparatus equipped with an eccentric substrate rotation device, and FIG. 5 is a conceptual diagram of the arrangement of small holes in the partition wall. The feature of this example is that the center of rotation of the substrate rotation device 13 is eccentric, and can be applied to larger substrates compared to the first embodiment. The other configurations and their operations are the same as in the first embodiment. As explained above, the device configuration according to the present invention allows the reactive gas concentration to be reduced to 10% in the discharge chamber and the thin film forming chamber.
You can make more than double the difference. Furthermore, since the plasma generated in the discharge chamber is blocked by the partition wall, there is almost no rise in substrate temperature or damage to the formed film due to ion bombardment. In addition, due to the presence of the partition wall, there is almost no chance of spatter particles adhering to the wall surface of the thin film forming chamber.
The reduction of reactive gas due to its getter action is extremely small, and the reactive gas is effectively used for the reaction of sputtered particles. Further, since the partition wall has a large number of small holes, the film thickness distribution can be easily made uniform by a combination of the arrangement thereof and the rotation of the substrate. Furthermore, since the small holes in the partition wall are long and narrow, the flying direction of the spatter particles can be kept at an opening angle of 45 degrees or less.

[Brief explanation of the drawing]

Fig. 1 is a side view of the configuration of an embodiment of the sputtering device according to the present invention, Fig. 2 is a conceptual diagram showing the arrangement of small holes in the partition wall, and Fig. 3 is a diagram showing the arrangement of the small holes and the rotation of the substrate. FIG. 4 is a diagram showing the film thickness distribution, FIG. 4 is a side view of the construction of an embodiment of the sputtering apparatus according to the present invention for a large substrate, and FIG. 5 is a diagram showing the arrangement of small holes formed in the partition walls. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Target, 3... Target support, 4... Substrate, 5... Substrate support,
6...Inert gas introduction device, 7...Reactive gas introduction device, 8, 9...Exhaust device, 10...Discharge power source, 11...Partition wall having small holes, 12...Flight direction of spatter particles , 13...Substrate rotation device, 11
1...Small hole, 112...Spiral for arranging the small hole.

Claims (1)

[Claims] 1. A target and a substrate facing the target are provided in a vacuum chamber, and the chamber is made into an atmosphere of a mixed gas of an inert gas and a reactive gas, and a discharge is caused to occur between the target substance and the reactive gas. In a reactive sputtering device that forms a reactant on a substrate, a partition wall having a large number of small holes with a length of 1 to 20 times the hole diameter is provided between the target and the substrate, and a discharge chamber and a substrate are placed on the target side. A thin film formation chamber is formed on the side, and an inert gas introduction device that introduces an inert gas into the discharge chamber is connected to an exhaust device that exhausts the air, and a reactive gas introduction device that introduces a reactive gas into the thin film formation chamber and an exhaust A reactive sputtering device characterized in that it is connected to an exhaust device that 2 A target and a substrate facing it are placed in a vacuum chamber, and the chamber is made into a mixed gas atmosphere of an inert gas and a reactive gas, and a discharge is caused to cause a reaction substance between the target substance and the reactive gas to be transferred onto the substrate. In a reactive sputtering device for forming a thin film, a partition wall having a large number of small holes with a length 1 to 20 times the hole diameter is provided between the target and the substrate, and a discharge chamber is formed on the target side and a thin film formation chamber is formed on the substrate side. The inert gas introduction device that introduces inert gas into the discharge chamber is connected to the exhaust device that exhausts the air, and the reactive gas introduction device that introduces reactive gas into the thin film formation chamber and the exhaust device that exhausts the air are connected. A reactive sputtering apparatus further comprising a substrate rotation mechanism for rotating the substrate within the thin film forming chamber.