JP2976382B2 - Sputtering method and sputtering apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering method and a sputtering apparatus, and in particular, monitors a potential of a plasma and controls each potential of a substrate and a target so that re-sputtering is not performed on the substrate. And a sputtering apparatus.

[Conventional technology]

In recent thin film techniques, a complex compound composed of two or more elements is often formed into a thin film by sputtering. For example, for example, Y ₁ Ba ₂ Cu ₃ O
There is an oxide superconductor such as _7-X , which is a compound composed of four elements, Y, Ba, Cu and O. In the field of oxide superconductors, in addition to this, La-Ba-Cu-O, Bi-Sr-
Many systems such as Ca-Cu-O system and Tl-Ca-Ba-Cu-O system are known, and it is well known that all of them are complex system compounds. Compounds of such a complex system are not limited to the field of oxide superconductors but also in the field of transparent conductive films, for example, and In ₂ O ₃ + SnO ₂ (abbreviation: ITO) is a typical example. is there. Further, transparent conductive films such as In ₂ O ₃ , SnO ₂ , and ZnO are also examples of the compound thin film.

For the production of a thin film of the above compound, a sputtering method which is excellent in mass productivity and easy to increase in area is generally used.

By the way, in making a thin film using the sputtering method,
There is a characteristic that a negative ion having a large mass is easily released by a substance to be sputtered. For example, when sputtering a target material such as the above-described oxide superconductor or ITO, oxygen negative ions O ⁻ are easily released. Here, FIG. 5 shows a normal potential distribution between the target and the substrate when the substrate in the conventional sputtering apparatus is grounded. V _T and V _P shown in the figure each represent a potential and the plasma potential targets.
Therefore, as described above, the negative ions emitted from the target are accelerated in a direction perpendicular to the target surface by the potential difference between the target and the plasma shown in FIG. 5, fly in the plasma space, and then move between the plasma and the substrate. And is incident on the substrate. Negative ion energy incident on the substrate, when grounded substrate, the energy corresponding to the potential V _T of the target. By the way, when ions bombard a substance, there is a threshold value that causes a sputtering phenomenon with respect to the ion energy. If the potential difference that gives this threshold energy is V _TH ,
In the conventional sputtering method, V _T is set to be | V _T | ≫ | V _TH |. Therefore, the film on the substrate is re-sputtered by the film impact of negative ions, and in the case of a compound target, the composition of the film deviates from the composition of the target, and in extreme cases, the film does not adhere to the entire surface of the substrate. There is a possibility that the substrate and the film may be damaged in a broad sense. Therefore, in order to suppress the re-sputtering of the film due to the negative ion bombardment, conventionally, a negative voltage V _S is applied to the substrate to reduce the energy (| V _T −V _S | ) Is made smaller than the energy equivalent to _VTH .

[Problems to be solved by the invention]

However, or by changing the sputtering conditions in the conventional sputtering method, according to the method of applying a voltage to the substrate, resulting in a problem that the voltage V _P of the plasma shown in FIG. 5 is changed. Then, in the conventional sputtering method, since this does not monitor the change of the plasma voltage V _P, it can not be accurately controlled energy of ions incident on the substrate, due to the negative ions by applying a voltage to change or substrate sputtering conditions Even if the film bombardment can be suppressed, as a result, the plasma potential _VP becomes high, causing a problem that resputtering of the film due to film bombardment of positive ions in the plasma cannot be ignored.

An object of the present invention is to control the energy of positive or negative ions incident on a substrate by adjusting the relationship between predetermined voltages in a sputtering apparatus while monitoring the state of a plasma, so that resputtering of the film does not occur. It is to provide a sputtering method and a sputtering apparatus for forming a film.

[Means for solving the problem]

The sputtering method according to the present invention is a sputtering method in which a voltage is independently applied to each of a target and a substrate disposed to face each other in a vacuum vessel, and a plasma is generated in a space between the target and the substrate. Target potential V _T , substrate potential V _S , plasma potential
V _P , when the threshold voltage of the occurrence of the sputtering action with respect to the acceleration voltage of the ions determined by the material and ion species of the target is V _TH , the potential V _P of the plasma is measured, this V _P and the above V _T, V _S, and the _{V TH, | V P -V T} |> | V TH | | V S -V T | <| V TH | | V P -V S | <| V TH | of relationship Is configured to control each applied voltage of the target and the substrate so that

In the sputtering method according to the present invention, it is preferable to control the electric potential V _T of the target priority.

The sputtering apparatus according to the present invention includes a vacuum vessel, a target and a substrate disposed opposite to each other in the vacuum vessel, a gas introduction system and a gas exhaust system attached to the vacuum vessel, and a target and a substrate. In a sputtering apparatus having a target power supply and a substrate power supply that independently apply a voltage and generate plasma in a vacuum chamber, a measurement apparatus that measures the potential of the plasma, and a plasma measurement apparatus that measures the potential of the plasma. A potential is input, this potential is V _P , the potential of the target is V _T , the potential of the substrate is V _S , and the threshold value of the sputtering phenomenon with respect to the ion acceleration voltage determined by the target material and the ion species is V _TH . _{when, | V P -V T |>} | V TH | | V S -V T | <| V TH | | V P -V S | <| V TH | of Mitsurusu so the relationship to, and the target power Output power of each board power supply Configured with a control means for independently controlling.

In the sputtering device according to the present invention, it is preferable to use an emissive probe as the measuring device.

[Action]

In the above method and apparatus according to the present invention, the sputtering has a configuration for measuring the potential of the plasma generated in the space between the target and the substrate, and the measured plasma potential, the target potential and the substrate potential, and the sputtering phenomenon. The target potential and the substrate potential are controlled so as to satisfy a predetermined magnitude relationship between the threshold voltage and the occurrence of resputtering due to ions on the substrate. That is, the target potential and the substrate potential are appropriately controlled. In the sputtering apparatus having the configuration described above, a configuration for monitoring the state of generated plasma is provided, so that a predetermined relationship is satisfied between the plasma potential, the target potential, the substrate potential, and the threshold voltage of the sputtering phenomenon. Feedback to the target potential and substrate potential Control is performed.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In the following drawings, the same elements are denoted by the same reference numerals, and the device configuration such as a gas introduction system and an exhaust system, a target holder, and a substrate holder required for the sputtering apparatus is the same as that of the conventional apparatus. Therefore, their illustration and description are omitted.

FIG. 1 is a schematic configuration diagram showing a first embodiment of the sputtering apparatus according to the present invention. In FIG. 1, 1 is a vacuum vessel, 2 is a target, 3 is a substrate,
And a space in which plasma is generated is formed between them. Reference numeral 4 denotes a DC power supply for applying a voltage (V _T ) to the target 2 to generate plasma in the space, and reference numeral 5 denotes a DC power supply for controlling the potential (V _S ) of the substrate 3. The DC power supplies 4 and 5 are both variable power supplies that can change the output voltage. Reference numeral 6 denotes a device for measuring the potential ( _VP ) of the plasma. This device 6 includes, for example, a filament 61, a DC power supply 62 for the filament, and resistors 63 and 64 having the same resistance value (the center of the filament 61 becomes the probe potential). This is an emissive probe including a DC power supply 65 and an ammeter 66 for varying the potential ( _VP ) of the probe. The detailed description of the emissive probe is omitted in the literature such as "Basic of Plasma Diagnosis-Plasma and Nuclear Fusion Society-" (Nagoya University Press) and so on, and therefore will be omitted. With this probe,
By changing 65, the voltage value of the power supply 65 when the current does not flow through the ammeter 66 becomes the plasma potential ( _VP ) to be obtained. (Actually, the difference is slightly different, but this difference is practically negligible.) As is apparent from the above-described configuration, in the sputtering apparatus according to the present embodiment, the plasma generated in the space between the target 2 and the substrate 3 is generated. and a Emissive probe 6 for measuring the potential V _P. In addition, the sputtering device has two control systems. The first control system is constituted by a controller 7, which reads the measured current value of the ammeter 66 and adjusts the output voltage of the power supply 65 so that the value becomes zero. The second control system includes a plasma potential reader 8 for reading the value of the output voltage of the variable DC power supply 65 and a controller 9. Controller 9
By plasma potential V _P obtained in plasma potential reader 9, the target 2 so as to satisfy the below conditions potential
In order to control the potential V _S of V _T and the substrate 3, the variable DC power supply 4 and 5
Are supplied with control signals S ₁ and S ₂ .

Next, a sputtering method performed by the sputtering apparatus having the above configuration will be described. In carrying out sputtering, by adjusting the output of the variable DC power supply 4 and 5, in order to generate a plasma in the space between the target 2 and the substrate 3, the target 2 a potential V _S of the potential V _T and the substrate 3 Set to the required potential value. When plasma is generated, the potential V _P of the plasma is
Is measured. The measured plasma potential V _P is read by the plasma potential reader 8, it is input to the controller 9. By measuring the potential V _P of the plasma generated in the vacuum vessel 1, the relationship potential between the target 2 and the substrate 3 that can know, to know the energy of the ions thereby incident on the substrate 3 it can.

The controller 9 controls the potential V _S of the potential V _T and the substrate 3 of the target 2 based on the potential V _P of the input plasma so as to satisfy a predetermined condition. That is, the potential of the plasma is V _P , the potential of the target 2 is V _T , the potential of the substrate 3 is V _S, and the threshold value of the sputtering phenomenon with respect to the ion acceleration voltage determined by the target material and ion species
_Assuming V _TH , the controller 9 determines these V _P , V _T , V _S , V _{TH
There, | V P -V T |>} | V TH | | V S -V T | <| V TH | | V P -V S | <| V TH | so as to satisfy the relational expression, the target potential V _T , Substrate voltage
Controls the output voltage of variable DC power supplies 4 and 5 that determine V _S.

Next, the reason why the above relational expression is required will be described. In sputtering, the energy potential V _P and the potential V _T of the target 2 in the plasma when the positive ions in the plasma are incident on the target 2 is the energy corresponding to the potential difference, the energy to sputter targets 2 _Therefore , the energy must be larger than the energy corresponding to the threshold value _VTH described above. That give this _{condition, | V P -V T |>} | a relationship | V _TH.

Next, the negative ions released from the target 2
Are accelerated by the potential difference between the potential V _T and the plasma potential V _P of the target 2, is then decelerated by a potential difference between flying into the plasma space potential V _S of potential V _P and the substrate 3 of the plasma incident on the substrate. Negative ion energy incident on the substrate 3 thus, (V _P -V _T) - with _{(V P -V S) = V} S -V T, i.e. the potential V _S of the potential V _T and the substrate 3 of the target 2 Energy corresponding to the potential difference is obtained. In order for the negative ions incident on the substrate 3 not to resputter the film on the substrate 3, the energy at the time of incident on the substrate 3 must be equal to the threshold V
_It must be less than the energy equivalent to _TH . The relational expression of | V _S −V _T | <| V _TH | gives this condition.

Finally, the positive ions in the plasma be incident on the substrate 3 are accelerated by the potential difference between the potential V _S of potential V _P and the substrate 3 of the plasma, giving the condition for not re-sputtered film on the substrate 3 but, | which is a relational expression _{| V P -V S | <|} V TH.

As described above, in the sputtering method according to the present invention, to monitor the plasma potential V _P, so as to satisfy the three relational expressions of the the controller 9, the variable DC power supply 4 and 5
, The voltage applied to the target 2 and the voltage applied to the substrate 3 are controlled, whereby the energy of ions incident on the substrate 3 can be controlled, and the film does not re-sputter. Can be performed.

When a conventional sputtering method performs deposition of Y-based oxide superconductor, as stated previously, O from the target ^- or Ar and O ₂ as A _r ⁺ or O ₂ ⁺ (generally the sputtering gas in the plasma The composition of the film significantly deviates from the composition of the target due to film impact by
Superconducting film cannot be obtained. In a Y-based oxide superconductor,
The threshold value V _TH of the energy of the incident ion that causes the sputtering phenomenon is almost the same for the incident ion such as O ⁻ , _Ar ⁺ , and O ₂ ⁺ , and is about 50 eV. On the other hand, the voltage applied to the target 2 and the substrate 3 is controlled by using the sputtering method of the present invention so that the above three relational expressions are satisfied. For example, V _T = −70 V, V _S = −30 V, V _P = +
When a sputtering film is formed at 5 V, a film without deviation from the target composition can be formed, and a superconducting film can be obtained with good reproducibility. The same applies to other substances,
For example, in the case of ITO, a film having a lower specific resistance than a film obtained by a conventional method can be obtained. In the sputtering method according to the present invention, the potential V _T of the target 2, in order to satisfy the three relations above, it must be controlled to be higher than the target potential in the conventional sputtering method. For that purpose, the voltage of the DC power supply 4 shown in FIG. 1 may be reduced. However, when DC discharge is performed using the DC power supply 4 shown in FIG. In some cases, discharge cannot be maintained depending on the type and the sputtering conditions such as pressure. Therefore, in such a case, a magnet 10 is disposed behind the target 2 to cause a magnetron discharge,
Configured to increase the potential V _T of the target 2.

FIG. 2 shows a high-frequency power supply 11 instead of the DC power supply 4 of FIG.
FIG. 3 is a schematic diagram of an embodiment using an impedance matching circuit 12 for applying power from the high-frequency power supply 11 without loss. Reference numeral 13 in the figure denotes a low-pass filter for blocking high frequencies from flowing to the DC power supply 5. When using high frequency as a plasma generating means as shown in FIG. 1, by increasing the frequency of the high frequency power source 11 can be increased potential V _T of the target 2, the discharge is also likely to be maintained in addition. Thus, depending on the plasma potential V _P obtained in device 6 for measuring the plasma potential, to control the potential V _T and the potential V _S of the substrate of the target 2, as shown in FIG. 1 DC discharge It is more convenient to use a high frequency discharge as shown in FIG. Also,
When a DC discharge is used as shown in FIG. 1, the target 2 must be a conductor, whereas when a high-frequency discharge is used as shown in FIG. 2, the target 2 may be an insulator. However or a substrate 3 is insulating, when the film to be produced is an insulator, will be cause charge-up at the DC power source 5 at the film surface as shown in FIG., It can not be controlled potential V _S of the substrate 3. In such a case, the voltage applied to the substrate 3 is controlled using a high frequency power supply 15 and an impedance matching circuit 16 as shown in FIG.

4 shows a configuration in which the allow control of the potential V _T of the target 2 easier in the embodiment shown in Figure 2. In this embodiment, the high frequency power source 11 is used as the means for generating the plasma by increasing the frequency, obtained by the control of this separately independent of the plasma generating means of the target 2 potential V _T to perform the DC power supply 4 is there. In the figure
17 is a low-pass filter.

In the above respective embodiments, in either showed Emissive probe as an apparatus 6 for measuring the plasma potential V _P, but other measurement methods such as described in the literature. However, if the potential V _S of the potential V _T and the substrate 3 of the target 2 wants to automatic control, who using Emissive probe that can measure the plasma and potential V _P in real time, the control faster than other measurement methods it can.

The sputtering method of the present invention employs a three-electrode sputtering or a four-electrode sputtering in which a voltage can be applied to a substrate (in this case, since a voltage is also applied to the substrate, 4-pole sputtering,
(May be better referred to as pentapole sputtering).

In the respective embodiments, the control target of the controller 9 is the target potential V _T and the substrate potential V _S, these need not necessarily be adjusted equally. For example preferentially controlling V _T, then may be configured to control the V _S as needed. In actual control, such control is preferable.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the target potential, the substrate potential, the plasma potential, and the threshold value are set to have a predetermined relationship while monitoring the plasma potential in the sputtering method. Can prevent resputtering of
Film formation can be performed with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of a sputtering apparatus according to the present invention, FIG. 2 is a block diagram of a second embodiment of the sputtering apparatus, and FIG.
FIG. 4 is a partial configuration diagram of a modified embodiment of the device, FIG. 4 is a configuration diagram of a third embodiment of the device, and FIG. 5 is a diagram for explaining a conventional problem. [Explanation of Symbols] 1 ... Vacuum container 2 ... Target 3 ... Substrate 4,5 ... Variable DC power supply 6 ... Device for measuring plasma voltage 7,9 ... Controller 8 ... Plasma potential reader 11, 15 High-frequency power supply 12,16 Impedance matching circuit 13,17 Low-pass filter

Claims (4)

(57) [Claims] 1. A sputtering method for independently applying a voltage to each of a target and a substrate disposed facing each other in a vacuum vessel to generate plasma in a space between the target and the substrate, The potential of the target is V _T , the potential of the substrate is V _S , the potential of the plasma is V _P , and the threshold voltage of the sputtering action generation with respect to the acceleration voltage of ions determined by the material and ion species of the target is V _TH. when the measures the potential V _P of the plasma, and this V _P, the V _T, V _S, V _TH
DOO _{is, | V P -V T |>} | V TH | | V S -V T | <| V TH | | V P -V S | <| V TH | a relationship to Mitsurusu so, the target And a method for controlling each applied voltage of the substrate. 2. A sputtering method according to claim 1, wherein, the sputtering method characterized by controlling the potential V _T of the target priority. 3. A vacuum vessel, a target and a substrate disposed in the vacuum vessel so as to face each other, a gas introduction system and a gas exhaust system attached to the vacuum vessel, and each of the target and the substrate. In a sputtering apparatus including a target power supply and a substrate power supply that independently apply a voltage and generate plasma in the vacuum vessel, a measurement apparatus that measures the potential of the plasma, and a potential of the plasma that is measured by the measurement apparatus. enter a, the electric potential V _P, potential V _T of the target potential V _S of the substrate, the threshold for sputtering phenomenon for ion acceleration voltage determined from the target material and ion species V
When the _{TH, | V P -V T |} > | V TH | | V S -V T | <| V TH | | V P -V S | <| V TH | of Mitsurusu so the relationship to, Control means for controlling output voltages of the target power supply and the substrate power supply independently of each other. 4. The sputtering device according to claim 3, wherein said measuring device is an emissive probe.