JP3127836B2 - Sputtering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming speed for forming a high dielectric film having a perovskite structure composed of a composite oxide of Ba, Sr and Ti used for a thin film for a capacitor such as a semiconductor memory. The present invention relates to a sputtering method with little change over time.
Ba, Sr and T having a conductivity of less than 00 mΩcm
The present invention relates to a sputtering method in which a film formation rate is less changed with time when a dielectric film is formed using a target made of a composite oxide of i.

[0002]

2. Description of the Related Art Generally, a high dielectric film having a perovskite structure composed of a composite oxide of Ba, Sr and Ti (hereinafter referred to as a BaSrTi composite oxide) is used as a thin film for a capacitor such as a semiconductor memory. It is known that a high dielectric film having a perovskite structure made of this BaSrTi composite oxide is formed by a sputtering method. In forming the high dielectric film by a sputtering method, the film forming speed changes with time.
Therefore, various sputtering methods have been proposed in order to prevent the deposition rate from changing over time.

[0003] As one of the sputtering methods for preventing the deposition rate from changing over time, there is known a method of performing DC or high-frequency magnetron sputtering using a target made of a BaSrTi composite oxide having a conductivity of 100 mΩ to 10 Ωcm. (Japanese Patent Laid-Open No. 7-10956
No. 6). Further, as a method of sputtering at a high and stable film forming rate, a method of performing sputtering by discharging electric power obtained by superimposing high-frequency electric power on DC electric power is also known (see JP-A-7-126845).

[0004]

A target having high conductivity can be sputtered at high speed by applying a high electric power. However, a target having high conductivity of less than 100 mΩcm has a time-dependent change in the deposition rate. This inevitably occurs, and furthermore, the deposition rate varies, and a high dielectric film made of a BaSrTi composite oxide having a uniform thickness cannot be obtained.

[0005]

Means for Solving the Problems Accordingly, the present inventors have:
Ba, Sr and T having high conductivity of less than 100 mΩcm
As a result of conducting research to develop a sputtering method in which the time-dependent change in the film formation rate is extremely small even when high-speed sputtering film formation is performed by applying a high DC power to a target made of a composite oxide of i, the results are as follows: (a) Conductivity of less than 100 mΩcm Ba and Sr having properties
And a sputtering method for forming a dielectric film using a target composed of a composite oxide of Ti,
The derivative of the DC discharge voltage with respect to the DC discharge power density is 1.
5 to 15 cm ² / A (preferably, 4~10cm ² /
400A having a DC power controlled so as to be in a discharge characteristic region within the range of A) and a constant discharge current density, or having a cycle in which the target has a positive potential in the DC power.
When sputtering is performed by discharging electric power with alternating power of KHz or less superimposed, the time-dependent change in the film forming rate is extremely small. (B) The DC discharge power density is 1.5 to 7 W / cm ²
It was found that it is preferable to be within the range.

The present invention has been made based on this finding, and (1) Ba, Sr having a conductivity of less than 100 mΩcm.
And a sputtering method for forming a dielectric film using a target composed of a composite oxide of Ti,
The derivative of the DC discharge voltage with respect to the DC discharge power density is 1.
5 to 15 cm ² / A (preferably, 4~10cm ² /
A) A sputtering method of performing sputtering by discharging DC power controlled so as to be in the discharge characteristic region within the range of A) and to keep the discharge current density constant, (2) Ba, Sr having a conductivity of less than 100 mΩcm
And a sputtering method for forming a dielectric film using a target composed of a composite oxide of Ti,
The derivative of the DC discharge voltage with respect to the DC discharge power density is 1.
5 to 15 cm ² / A (preferably, 4~10cm ² /
A) A power obtained by superimposing an alternating power of 400 KHz or less having a period in which the target becomes a positive potential on a DC power controlled so as to be in the discharge characteristic region within the range of A) and to keep the discharge current density constant. A sputtering method for performing sputtering.

[0007] The DC discharge power density is a value obtained by dividing discharge power for sputtering by a target area, and the value is preferably in the range of 1.5 to 7 W / cm ² . Therefore, the present invention provides: (3) Ba, Sr having a conductivity of less than 100 mΩcm
And a sputtering method for forming a dielectric film using a target composed of a composite oxide of Ti,
The differential coefficient of the DC discharge voltage with respect to the DC discharge power density in the range of 1.5 to 7 W / cm ² is 1.5 to 15 cm ² / A
(Preferably, a sputtering method in which sputtering is performed by discharging DC power controlled so as to be in a discharge characteristic region within a range of 4 to 10 cm ² / A and a discharge current density is constant, (4) a sputtering method of less than 100 mΩcm Ba, Sr having conductivity
And a sputtering method for forming a dielectric film using a target composed of a composite oxide of Ti,
The differential coefficient of the DC discharge voltage with respect to the DC discharge power density in the range of 1.5 to 7 W / cm ² is 1.5 to 15 cm ² / A
(Preferably 4 to 10 cm ² / A) DC power controlled so as to be in a discharge characteristic range within a range of 4 to 10 cm ² / A and to keep the discharge current density constant, to 400 KHz or less having a cycle in which the target has a positive potential. A sputtering method in which sputtering is performed by discharging electric power on which alternating power is superimposed.

As described above, the conductivity is 100 mΩcm or less.
A target made of a BaSrTi composite oxide in the range of 10 Ωcm has no problem because the change with time of the film formation rate is extremely small even under a direct current or high-frequency magnetron sputtering under normal conditions, but there is no problem. When a target made of a BaSrTi composite oxide is subjected to direct current or high frequency magnetron sputtering for a long time, a constant film formation rate cannot be obtained due to a change in discharge impedance resulting from a long time film formation. Therefore, in order to obtain a constant film forming rate even when sputtering a target made of a BaSrTi composite oxide having a diameter of less than 100 mΩcm according to the present invention for a long time, a sputtering method in which an anode in which electrons emitted from the target are stably absorbed is provided. Using a device, the differential coefficient of the DC discharge voltage to the DC discharge power density is 1.5 to 15 cm ²
/ A (preferably, 4 to 10 cm ² / A), and further has a DC power with a constant discharge current density or a period in which the target has a positive potential in the DC power. It is necessary to perform sputtering by discharging electric power on which alternating power of 400 KHz or less is superimposed.

As seen in the sputtering methods (2) and (4) above, when alternating power is superimposed on DC power, a 400 K
Using power superimposed with alternating power of less than or equal to
For example, INTERNATIONAL CONFERE
NCE ON METALLLURGICAL COAT
INGS AND THIN FILMS ICMCT
As disclosed in F93 (1993.3), this is a technique that is already known as a condition effective for suppressing the generation of fine dust and abnormal discharge, and therefore the explanation of the reason for the limitation is omitted.

[0010] In the sputtering method of the present invention,
The DC discharge power density was restricted to the range of 1.5～7W / cm ² and is, 1.5 W / derivative of DC discharge voltage for DC discharge power density in cm less than ² 15cm ² / A
Is not preferable because a stable film-forming rate cannot be obtained because of the above-mentioned problem. On the other hand, even if sputtering is performed at a DC discharge power density exceeding 7 W / cm ² , cracks are generated in the target, which is not preferable. Things. The target used in the present invention, which is composed of a composite oxide of Ba, Sr and Ti having a conductivity of less than 100 mΩcm, has a component composition in which _y in (Ba ₁ -xSr _x ) TiO y is approximately 2.97 or less. Can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Commercially available BaCO ₃ powder, SrCO ₃ powder and Ti
O ₂ powder was prepared and these BaCO ₃ powder, SrCO ₃
The powder and the TiO ₂ powder are blended, put in a ball mill and mixed, and the obtained mixed powder is fired in the atmosphere at 1100 ° C. for 1 hour to obtain (Ba _0.5 Sr
_0.5 ) A composite oxide of TiO _3.00 was prepared.

This composite oxide is put into a ball mill and pulverized to produce a composite oxide powder having an average particle size of 0.3 μm, and the obtained composite oxide powder is filled in a graphite mold, and the temperature is increased. : 5 ° C / min, heating temperature: 1300 ° C, pressure: 150 kgf / cm ² , holding time: 1 hour, cooling: furnace cooling, diameter: 13
A hot-pressed body made of a (Ba _0.5 Sr _0.5 ) TiO _2.97 composite oxide having a size of 5 mm and a thickness of 6 mm, and each having a relative density of 99% or more, is produced, and the hot-pressed body is machined. Thus, a target having a size of 125 mm in diameter and 5 mm in thickness was produced. The resistance value of the obtained target was 80 mΩcm.

Example 1 This target was bonded to a water-cooled copper plate with In-Sn solder, set in a DC magnetron sputtering apparatus provided with an anode, and an atmosphere gas: a mixed gas of Ar and oxygen (Ar: O = 1: 1).
1) Sputter gas pressure: 15 mTorr Substrate-target distance: 5 cm Initial DC discharge power density (P): 2.5 W / cm ² Derivative coefficient (dV) of DC discharge voltage (V) with respect to initial DC discharge power density (P) / DP): 8.0 cm ² / A Fixed discharge current density: 0.0124 A / cm ² Sputtering time: 25 hours Sputtering was carried out under the following conditions: Continuous discharging time: Deposition rate every 5 hours (angstrom / min) Was measured and the relationship between the film formation rate and the continuous discharge time was plotted to create a graph. The graph is shown in FIG. Further, during the 25-hour sputtering, abnormal discharges with a phenomenon time width of 100 μsec or less occurred about 50 times, but no abnormal discharges with a time width larger than this occurred. In addition, no damage was found on the target after the sputtering.

Comparative Example 1 Except that the derivative (dV / dP) of the DC discharge voltage (V) with respect to the DC discharge power density (P) was 22.9 cm ² / A, and the fixed discharge current density was 0.0063 A / cm ^2. Was sputtered under the same conditions as in Example 1, and a graph was created by plotting the relationship between the film formation rate (angstrom / min) and the continuous discharge time. The graph is shown in FIG.

Conventional Example 1 A target was joined to a water-cooled copper plate by In-Sn solder in the same manner as in Example 1, and set in a DC magnetron sputtering apparatus. Atmospheric gas: a mixed gas of Ar and oxygen (Ar: O = 1: 1)
1) Sputter gas pressure: 15 mTorr Substrate-target distance: 5 cm Fixed discharge power density: 2.5 W / cm ² Continuous discharge time: 25 hours Sputtering was performed under the following conditions, and the film formation rate (angstrom / min) was plotted to create a graph, and the graph is shown in FIG.

From the graph shown in FIG. 1, the diagram obtained in Example 1 shows that the film formation rate for a continuous discharge time of 25 hours is a minute change in the range of ± 3 Å / min, while The diagram obtained in Example 1 shows that the film formation rate with respect to a continuous discharge time of 25 hours is reduced by 20 Å / min or more at the initial stage, and the BaS having a constant thickness is formed.
It can be seen that a high dielectric film made of the rTi composite oxide cannot be obtained. Also, the initial DC discharge power density (P)
22.9c, the differential coefficient (dV / dP) of the DC discharge voltage (V) greatly deviated from 15 cm ² / A of the present invention.
In the diagram obtained in Comparative Example 1 performed at m ² / A, the change in the film formation rate (angstrom / min) with respect to the continuous discharge time is very small, but the efficiency is small because the value of the film formation rate is extremely small. It can be seen that the film cannot be formed easily, and is therefore not a practical method.

Example 2 This target was bonded to a water-cooled copper plate with In-Sn solder, and was set in a DC magnetron sputtering apparatus provided with an anode. Atmospheric gas: a mixed gas of Ar and oxygen (Ar: O = 1:
1) Sputter gas pressure: 15 mTorr Substrate-target distance: 5 cm Initial DC discharge power density (P): 3.3 W / cm ² Derivative coefficient (dV) of DC discharge voltage (V) with respect to initial DC discharge power density (P) / DP): 5.4 cm ² / A Fixed discharge current density: 0.0166 A / cm ² Frequency of superimposed alternating power having a cycle in which the target potential becomes +50 V: 100 KHz Continuous discharge time: 25 hours Continuous discharge time: The film formation rate (angstrom / min) was measured every 5 hours, and a graph was created by plotting the relationship between the film formation rate and the continuous discharge time. The graph is shown in FIG. Further, during the 25-hour sputtering, abnormal discharge with a time width of 100 μsec or less occurred three times within 15 minutes after the start of discharge, but thereafter, no abnormal discharge occurred. The time width of the phenomenon is 100
Abnormal discharge for more than μsec never occurred. After the end of sputtering, no damage was found on the target.

Comparative Example 2 The derivative (dV / dP) of the DC discharge voltage (V) to the DC discharge power density (P) was 18.9 cm ² / A, and the fixed discharge current density was 0.0071 A / cm ^2. Was sputtered under the same conditions as in Example 2, and a graph was created by plotting the relationship between the film formation rate (angstrom / min) and the continuous discharge time. The graph is shown in FIG.

Conventional Example 2 A target was bonded to a water-cooled copper plate by In-Sn solder in the same manner as in Example 2, and was set in a DC magnetron sputtering apparatus. Atmospheric gas: a mixed gas of Ar and oxygen (Ar: O = 1: 1)
1) Sputter gas pressure: 15 mTorr Substrate-target distance: 5 cm Fixed discharge power density: 3.3 W / cm ² Frequency of superimposed alternating power having a cycle where the target potential is +50 V: 100 KHz Continuous discharge time: 25 hours Sputter under the conditions and the film formation rate (angstrom /
A graph was created by plotting the relationship between the continuous discharge time and the discharge time of the continuous discharge time (min), and the graph is shown in FIG.

From the graph shown in FIG. 2, the diagram obtained in Example 2 shows a small change in the film formation rate within a range of ± 2 Å / min with respect to a continuous discharge time of 25 hours. The diagram obtained in the conventional example 2 shows that the film formation rate with respect to the continuous discharge time of 25 hours is reduced by 30 Å / min or more at the initial stage, and the Ba having a constant thickness is obtained.
It can be seen that a high dielectric film made of the SrTi composite oxide cannot be obtained. Also, the derivative (dV / d) of the DC discharge voltage (V) with respect to the initial DC discharge power density (P)
P) deviates greatly from 15 cm ² / A of the present invention.
The diagram obtained in Comparative Example 2 performed at 8.9 cm ² / A shows the film formation rate (angstrom / mi) with respect to the continuous discharge time.
Although the change in n) is very small, the value of the film formation rate is extremely small, indicating that efficient film formation cannot be performed, and thus it is not a practical method.

Examples 3 to 11 DC discharge power density (P), differential coefficient (dV / dP) of DC discharge voltage (V) with respect to DC discharge power density (P), and fixed discharge current density are shown in Table 1. Sputtering was carried out under the same conditions as in Example 1 except that the film formation rate (angstrom / m) immediately after the start of film formation and after 25 hours of continuous discharge time
in) was measured, and the results are shown in Table 1. From the results shown in Table 1, Examples 3 to 1 satisfying the conditions of the present invention are shown.
It can be seen that the difference between the film formation rates immediately after the start of film formation in Example 1 and the continuous discharge time: 25 hours after was very small.

[0021]

[Table 1]

Examples 12 to 21 DC discharge power density (P), differential coefficient (dV / dP) of DC discharge voltage (V) with respect to DC discharge power density (P), and fixed discharge current density are shown in Table 2. Sputtering was carried out under the same conditions as in Example 2 except that the film formation rate (angstrom / m) immediately after the start of film formation and after 25 hours of continuous discharge time
in) was measured, and the results are shown in Table 2. From the results shown in Table 2, Examples 12 to which satisfy the conditions of the present invention are shown.
It can be seen that the difference between the film formation rates immediately after the start of film formation at 21 and the continuous discharge time: 25 hours after was small.

[0023]

[Table 2]

[0024]

As described above, in the sputtering method of the present invention, since the film formation rate does not change with time, a high dielectric film made of a BaSrTi composite oxide having a uniform thickness can be obtained even when the sputtering is performed for a long time. It has excellent industrial effects.

[Brief description of the drawings]

FIG. 1 is a graph plotting the relationship between the film formation rate and the continuous discharge time obtained in Example 1, Comparative Example 1, and Conventional Example 1.

FIG. 2 is a graph plotting the relationship between the film formation rate and the continuous discharge time obtained in Example 2, Comparative Example 2, and Conventional Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 21/316 H01L 21/316 Y 21/8242 27/10 651 27/108 (58) Investigated field (Int.Cl. ⁷ , (DB name) C23C 14/00-14/58 H01L 21/203 H01L 21/285 H01L 21/31 H01L 21/316 H01L 21/8242 H01L 27/108 H05H 1/46

Claims (3)

(57) [Claims] 1. B having a conductivity of less than 100 mΩcm
In a sputtering method for forming a dielectric film using a target composed of a composite oxide of a, Sr and Ti, a differential coefficient of DC discharge voltage to DC discharge power density is 1.
A sputtering method characterized in that sputtering is performed by discharging DC power controlled so as to have a discharge characteristic region within a range of 5 to 15 cm ² / A and a constant discharge current density. 2. B having a conductivity of less than 100 mΩcm
In a sputtering method for forming a dielectric film using a target composed of a composite oxide of a, Sr and Ti, a differential coefficient of DC discharge voltage to DC discharge power density is 1.
DC power controlled so that the discharge characteristics are in the range of 5 to 15 cm ² / A and the discharge current density is constant, 400K having a period in which the target has a positive potential.
A sputtering method characterized in that sputtering is performed by discharging electric power in which alternating power of not more than Hz is superimposed. 3. The DC discharge power density is 1.5 to 7 W /
^3. The sputtering method according to claim 1, wherein the thickness is in the range of cm ² .