Sputtering apparatus and sputtering method

Abstract

To provide a sputtering device by which a nitrogen thin film can be stably formed with an accurate composition ratio of the film, and to provide a sputtering method.SOLUTION: A sputtering device includes: a vacuum chamber in which a target material and a substrate can be disposed so as to face each other; a DC power supply electrically connectable with the target material; a gas supply source introducing film deposition gas containing nitrogen gas into the vacuum chamber; and a pulsed unit pulsing an electric current flowing in the target material from the DC power supply. Using a sintered alloy target material of a binary or more compound as the target material, plasma is generated in the vacuum chamber to form a nitride thin film having a ternary or more compound containing nitrogen on a substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sputtering apparatus and a sputtering method for depositing a nitride resistor thin film on a substrate such as a semiconductor wafer. [Background technology]

[0002] In recent years, there has been a demand for devices such as resistors and thermistors, which are made by depositing thin films on substrates in desired patterns, with a higher resistance range. This has led to a growing need for technology to form nitride thin films, which have higher resistivity than alloy-based materials such as nichrome.

[0003] In general, from the viewpoint of production speed and production stability, nitride thin films are often formed by reactive sputtering, in which deposition is caused by reacting a target material, which is a raw material, with a reactive gas. Conventionally, there is a sputtering method in which the degree of nitridation is controlled by the flow rate of nitrogen, which is a reactive gas, and the film formation pressure (see, for example, Patent Document 1).

[0004] A conventional reactive sputtering method will now be described, primarily with reference to FIG. 12. FIG. 12 is a schematic cross-sectional view of a conventional reactive sputtering apparatus. A vacuum chamber 1 can be depressurized and evacuated to a vacuum state by evacuating it with a vacuum pump 2 connected via a valve 3. A gas supply source 4 can supply a nitrogen-containing gas to the vacuum chamber 1 at a constant rate. The degree of vacuum in the vacuum chamber 1 can be controlled to a desired gas pressure by changing the opening and closing ratio of the valve 3. A target material 7 is placed in the vacuum chamber 1. A backing plate 8 supports the target material 7. A DC power supply 30 is electrically connected to the backing plate 8. By applying a voltage to the target material 7 via the backing plate 8, a portion of the gas in the vacuum chamber 1 dissociates, generating plasma. A substrate 6 is placed in the vacuum chamber 1 facing the target material 7. A substrate holder 5 is placed below the substrate 6 and supports the substrate 6.

[0005] The target material 7 is sputtered by the plasma generated in the vacuum chamber 1 and flies out, reaching the substrate 6 where a thin film of the target material 7 is deposited. At the same time, the gas and plasma in the vacuum chamber react with the target material 7 being deposited on the substrate, resulting in a nitride thin film.

[0006] The proportion of nitrogen contained in the nitride thin film is correlated with electrical properties such as resistivity and its temperature coefficient (TCR), which are important in resistive devices. To achieve the desired electrical properties, the gas supplied from the gas supply source 4 is adjusted by adjusting the mixture ratio of nitrogen, which reacts with the thin film, and an inert gas such as argon, which does not react with the thin film. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2579470 Summary of the Invention [Problem to be solved by the invention]

[0008] However, with the conventional reactive sputtering apparatus described above (see Figure 12), it is difficult to precisely control the degree of nitridation of the thin film due to the resolution limit of the mass flow controller that sets the gas flow rate, and it is difficult to accurately adjust the resistivity and temperature coefficient TCR of the thin film to the desired values, making stable production difficult.

[0009] Furthermore, when forming a nitride thin film with ternary or more elements, such as a ternary metal A-metal Bx-nitrogen Ny, which can achieve higher resistivity, a metal AB alloy is used as the target material 7, and the resistivity and TCR vary depending on the AB ratio. This means that not only the degree of nitriding y but also the AB ratio x must be precisely controlled. However, if the AB ratio x of the raw material target material 7 varies during target manufacturing, the electrical characteristics will also change. Furthermore, when the target material 7 is worn out, the AB ratio x may change, causing changes in the electrical characteristics, further complicating stable production.

[0010] In consideration of the above-mentioned conventional problems, the present invention aims to provide a sputtering apparatus and a sputtering method that can control the composition ratio of a nitride thin film with high precision and can stably form the film. [Means for solving the problem]

[0011] The sputtering apparatus according to the present invention comprises: a vacuum chamber in which a target material and a substrate can be disposed facing each other; a DC power source electrically connectable to the target material; a gas supply source that introduces a film forming gas containing nitrogen gas into the vacuum chamber; a pulsing unit for pulsing the current flowing from the DC power supply to the target material; Equipped with A sintered alloy target material having a binary or more elemental composition is used as the target material, and plasma is generated in the vacuum chamber to form a nitride thin film having a ternary or more elemental composition containing nitrogen on the substrate.

[0012] A sputtering method according to the present invention includes the steps of: preparing a vacuum chamber in which a target material and a substrate can be disposed opposite each other; electrically connecting to the target material; introducing a film forming gas containing nitrogen gas into the vacuum chamber; detecting an emission spectrum of plasma generated in the vacuum chamber; calculating an emission intensity ratio between the target material and a deposition gas containing nitrogen gas from the position and intensity of the characteristic peak of the detected emission spectrum; a step of setting an ON / OFF time of a pulse based on the calculated emission intensity ratio of the deposition gas to pulse the current flowing through the target material; Includes. [Effects of the Invention]

[0013] The sputtering apparatus and sputtering method according to the present invention enable precise control of the composition of ternary or more nitride thin films by adjusting the pulse discharge conditions, thereby enabling fine adjustment to desired resistivity and TCR. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a sputtering apparatus according to a first embodiment. [Figure 2] 1(a) is a graph showing the relationship between the N2 gas flow rate ratio and the specific resistance in Comparative Example 1, and FIG. 1(b) is a partially enlarged view of a part of the graph in FIG. [Figure 3] 1A is a graph showing the relationship between the N2 gas flow rate ratio and TCR in Comparative Example 1, and FIG. 1B is a partially enlarged view of a portion of the graph in FIG. [Figure 4] 1A is a graph showing the relationship between pulse ON time and resistivity in the sputtering method according to Example 1, and FIG. 1B is a partially enlarged view of a portion of the graph in FIG. 1A. [Figure 5] 1A is a graph showing the relationship between pulse ON time and TCR in the sputtering method according to Example 1, and FIG. 1B is a partially enlarged view of a portion of the graph in FIG. 1A. [Figure 6] 4 is a graph showing the relationship between pulse ON time and the Si composition ratio in a CrSi alloy in the sputtering method according to Example 1. [Figure 7] FIG. 10 is a schematic cross-sectional view showing the configuration of a sputtering apparatus according to a second embodiment. [Figure 8]10A is a diagram showing an example of measurement of the plasma emission spectrum in the sputtering method according to the second embodiment; FIG. 10B is a partially enlarged view of the Si emission peak and the surrounding emission spectrum; FIG. 10C is a partially enlarged view of the Cr emission peak and the surrounding emission spectrum; FIG. 10D is a partially enlarged view of the N2 emission peak and the surrounding emission spectrum; and FIG. 10E is a partially enlarged view of the Ar emission peak and the surrounding emission spectrum. [Figure 9] FIG. 10 is a graph showing the resistivity and TCR of a nitride thin film formed in the second embodiment. [Figure 10A] 10 is a graph showing the relationship between the N 2 gas flow rate and TCR in the sputtering method according to Example 3, showing the case where the pulse ON time is controlled from the minimum to the maximum. FIG. [Figure 10B] 10 is a graph showing the relationship between the N2 gas flow rate and the specific resistance in the sputtering method according to Example 3, showing the case where the pulse ON time is controlled from the minimum to the maximum. FIG. [Figure 11A] FIG. 10 is a graph showing the relationship between the pulse ON time and the N2 emission intensity ratio in the sputtering method according to Example 4, where the N2 gas flow rate is changed. [Figure 11B] 10 is a graph showing the relationship between the pulse ON time and the Si emission intensity ratio in the sputtering method according to Example 4, showing the case where the N2 gas flow rate is changed. FIG. [Figure 12] FIG. 1 is a schematic cross-sectional view showing the configuration of a conventional sputtering apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] The sputtering apparatus according to the first aspect includes a vacuum chamber in which a target material and a substrate can be disposed facing each other; a DC power source electrically connectable to the target material; a gas supply source that introduces a film forming gas containing nitrogen gas into the vacuum chamber; a pulsing unit for pulsing the current flowing from the DC power supply to the target material; Equipped with A sintered alloy target material having a binary or more elemental composition is used as the target material, and plasma is generated in the vacuum chamber to form a nitride thin film having a ternary or more elemental composition containing nitrogen on the substrate.

[0016] A sputtering apparatus according to a second aspect is the sputtering apparatus according to the first aspect, further comprising: a viewport for observing plasma generated in the vacuum chamber; a spectrometer for detecting the emission spectrum of the plasma; an emission spectrum calculator that calculates an emission intensity ratio between the target material and a deposition gas containing nitrogen gas from the position and intensity of the characteristic peak of the detected emission spectrum; a pulse controller that sets pulse ON / OFF times in the pulsing unit based on the calculated emission intensity ratio of the deposition gas; may further comprise:

[0017] A sputtering method according to a third aspect is a sputtering method using the sputtering apparatus according to the first or second aspect, The composition ratio of two or more metals contained in the nitride thin film is changed by setting the pulse ON / OFF time of the pulsing unit.

[0018] With the above configuration, even if the composition varies depending on the lot of the target material or the target material is worn out after a long period of film formation, the gas flow rate and pulse conditions can be changed according to the state of the target material from the plasma emission spectrum. Therefore, since the variation in electrical characteristics is minimized, it becomes possible to stably form, for example, a nitride resistive thin film.

[0019] A sputtering method according to a fourth aspect is a sputtering method using the sputtering apparatus according to the second aspect, measuring the plasma generated in the vacuum chamber with the spectrometer; a step of normalizing the measured current value of the emission intensity of the emission peak of the plasma with a pre-recorded reference value of the emission intensity in the plasma state to obtain a normalized emission intensity; calculating an emission intensity ratio of nitrogen in the entire film forming gas; feedback-controlling the pulse ON time so that the difference between the reference value and the current value of the nitrogen emission intensity ratio is minimized; Includes.

[0020] A sputtering method according to a fifth aspect includes the steps of: preparing a vacuum chamber in which a target material and a substrate can be disposed opposite each other; electrically connecting to the target material; introducing a film forming gas containing nitrogen gas into the vacuum chamber; detecting an emission spectrum of plasma generated in the vacuum chamber; calculating an emission intensity ratio between the target material and a deposition gas containing nitrogen gas from the position and intensity of the characteristic peak of the detected emission spectrum; a step of setting an ON / OFF time of a pulse based on the calculated emission intensity ratio of the deposition gas to pulse the current flowing through the target material; Includes.

[0021] A sputtering method according to a sixth aspect is the same as that of the fifth aspect, wherein in the step of calculating the emission intensity ratio of the film formation gas, the emission intensity of the current value of the characteristic peak of nitrogen in the detected emission spectrum is normalized by a value of the emission intensity of nitrogen in a plasma state, which is a pre-recorded reference value, to calculate the normalized emission intensity of nitrogen; The method may further include a step of feedback-controlling a pulse ON time so that a difference between the reference value and the current value of the emission intensity ratio of nitrogen in the entire film formation gas is minimized.

[0022] Hereinafter, a sputtering apparatus and a sputtering method according to an embodiment will be described in detail with reference to the drawings, in which substantially the same components are designated by the same reference numerals.

[0023] (Embodiment 1) First, the configuration of a sputtering apparatus 10 according to the first embodiment will be described with reference mainly to Fig. 1. Fig. 1 is a schematic cross-sectional view showing the configuration of a sputtering apparatus 10 according to the first embodiment. This sputtering apparatus 10 includes a vacuum chamber 1, a DC power supply 30, a pulsing unit 32, and a pulse controller 41. A target material 7 and a substrate 6 can be placed inside the vacuum chamber 1, facing each other. The DC power supply 30 can be electrically connected to the target material 7. The pulsing unit 32 pulses the current flowing from the DC power supply 30 to the target material 7. The pulse controller 41 sets the pulse ON time and pulse OFF time in the pulsing unit 32. According to the sputtering apparatus 10 of the first embodiment, the composition of the ternary or more nitride thin film can be precisely controlled by adjusting the pulse discharge conditions by the pulse controller 41. This allows fine adjustment to the desired resistivity and TCR.

[0024] Each component of the sputtering apparatus 10 will be described below.

[0025] <Vacuum chamber> The vacuum chamber 1 can be depressurized to a vacuum state by evacuating it with a vacuum pump 2 connected via a valve 3 .

[0026] <Gas supply source> The gas supply source 4 is composed of a gas source such as a gas cylinder and a flow rate controller such as a mass flow controller, and is capable of supplying the gas required for sputtering at a constant rate to the vacuum chamber 1. The gas supplied by the gas supply source 4 can be selected from gases that are reactive with the target material, such as nitrogen or oxygen, or a mixed gas of a reactive gas with a rare gas such as argon.

[0027] <Valve> The degree of vacuum within the vacuum chamber 1 can be controlled to a desired gas pressure by changing the opening and closing rate of the valve 3.

[0028] <Target material> In FIG. 1, a target material 7 is placed in the upper part of the vacuum chamber 1. The target material 7 is a metal material with a composition of two or more elements. For example, a combination of silicon and a transition metal can be selected as a high-resistivity material. For example, silicon can be selected as metal A in a binary alloy AB, and tantalum, niobium, chromium, or the like can be selected as metal B. Note that the target material 7 can also contain oxygen within the range of its electrical conductor. This includes trace amounts of oxygen contained in a target formed by sintering atomized powder of the raw metal.

[0029] <Backing plate> The backing plate 8 supports the target material 7 .

[0030] <DC power supply> The DC power supply 30 is electrically connected to the target material 7 via the pulsing unit 32 and the backing plate 8, and is capable of applying a voltage to the target material 7.

[0031] <Pulse unit> The pulsing unit 32 stores the DC current generated by the DC power supply 30 in a built-in capacitor or the like, and pulses it by turning it on and off using a built-in semiconductor switching element or the like. A configuration in which the on / off switching can be set as a digital value can be selected, and the time setting resolution can be, for example, 1 μs or less.

[0032] <Pulse controller> The pulse controller 41 controls the on-time and off-time of the pulse to be instructed to the pulsing unit 32 based on the relationship between the pulse conditions for generating plasma and the electrical properties of the thin film.

[0033] <Magnet and yoke> The magnet 11 and yoke 12 are disposed on the rear surface of the backing plate 8 and can generate a magnetic field on the surface of the target material 7. One or more magnets 11 may be used. The magnet 11 may be either a permanent magnet or an electromagnet. The yoke 12 is connected to one end of the magnet 11, forming a magnetic circuit and preventing unnecessary leakage of the magnetic field to the side opposite the target material 7. The magnet 11 and yoke 12 concentrate plasma at a position where the magnetic field parallel to the plane of the target material 7 is at its maximum, thereby improving the deposition rate. This position where plasma is concentrated is called erosion. Furthermore, if erosion is concentrated at a specific position, only a portion of the target material 7 will be consumed, resulting in inefficient material utilization. Therefore, the erosion position may be moved by moving the magnet 11 and yoke 12 parallel to the surface of the target material 7 using a magnet rotation mechanism 20.

[0034] <Substrate and substrate holder> 1, a substrate 6 is disposed in the lower part of a vacuum chamber 1 so as to face a target material 7. A substrate holder 5 is disposed below the substrate 6 and supports the substrate 6.

[0035] (Operation of sputtering equipment) Next, the operation of the sputtering apparatus 10 according to the first embodiment will be described, and the sputtering method according to the first embodiment will also be described (the same applies to the other second embodiment). (1) First, the target material 7 is set in the vacuum chamber 1, and the substrate 6 is set below the target material 7 in a substantially horizontal position. (2) Next, the vacuum pump 2 is operated to reduce the pressure inside the vacuum chamber 1 to create a vacuum. After the predetermined vacuum level is reached, gas is introduced from the gas supply source 4, and the opening of the gate valve 3 is adjusted to achieve the predetermined gas pressure. (3) Next, a voltage is generated by the DC power supply 30, and the voltage is pulsed by switching the voltage at a predetermined on-time and off-time by the pulsing unit 32, and the pulsed voltage is applied to the target material 7, thereby generating plasma in the vacuum chamber 1. (4) The target material 7 is sputtered by the pulsed plasma generated in the vacuum chamber 1 and ejected, reaching the substrate 6 where a thin film containing the elements that make up the target material is deposited. At the same time, the gas and plasma in the vacuum chamber 1 react with the target material being deposited on the substrate 6. Furthermore, during the time when the voltage application is off, the gas and plasma in the vacuum chamber 1 react with the target material deposited on the substrate 6, forming a thin film of a compound formed by the reaction of the dense target material with the gas. A series of pulse depositions is repeated a predetermined number of times to deposit a nitride thin film on the substrate 6 .

[0036] (Comparative Example 1) In Comparative Example 1, a nitride thin film was formed using the conventional configuration shown in FIG. 12, that is, a configuration in which the DC power supply 30 was directly connected to the target material 7. At this time, the film formation conditions were an ultimate vacuum of 1×10 -4 Films were formed on glass substrates under conditions where the film deposition pressure was fixed at 0.45 Pa or less, the power of the DC power supply 30 was 100 W, the Ar gas flow rate was 15 sccm, and the nitrogen gas flow rate was varied in the range of 3.0 sccm to 5.5 sccm. In this case, the film deposition was performed under conditions where the flow rate was varied in increments of 0.1 sccm within the range of 3.8 sccm to 4.2 sccm, which was the minimum resolution of the mass flow controller used.

[0037] Example 1 In Example 1, a nitride thin film was formed using the configuration of Embodiment 1. At this time, the film formation conditions were an ultimate vacuum of 1×10 -4 Samples for resistance measurement were deposited on glass substrates under the following conditions: Ar gas flow rate was fixed at 15 sccm, nitrogen gas flow rate was fixed at 4.1 sccm, and pulse period (= pulse ON time + pulse OFF time) was set to 100 μsec, with the pulse ON time being varied in 1 μsec increments, which is the minimum resolution of the pulse controller used. Under some conditions, samples for composition analysis were deposited on sapphire substrates that did not contain Si.

[0038] FIG. 2(a) is a graph showing the relationship between the N2 gas flow rate ratio and the resistivity in Comparative Example 1, and FIG. 2(b) is a partially enlarged view of the graph in FIG. 2(a). FIG. 3(a) is a graph showing the relationship between the N2 gas flow rate ratio and the TCR in Comparative Example 1, and FIG. 3(b) is a partially enlarged view of the graph in FIG. 3(a). FIG. 4(a) is a graph showing the relationship between the pulse-ON time and the resistivity in the sputtering method according to Example 1, and FIG. 4(b) is a partially enlarged view of the graph in FIG. 4(a). FIG. 5(a) is a graph showing the relationship between the pulse-ON time and the TCR in the sputtering method according to Example 1, and FIG. 5(b) is a partially enlarged view of the graph in FIG. 5(a).

[0039] The thickness of the deposited thin film samples was measured using a stylus-type step gauge, and the sheet resistance was measured using the four-point probe method and calculated as sheet resistance [Ω / □] × film thickness [cm] = resistivity [Ω·cm]. Similar resistance measurements were also performed on the samples while they were heated on a hot plate, and the slope of the resistance change with temperature, ΔR ÷ R0 ÷ ΔT [ppm / °C], was calculated. The temperatures for resistance measurement were 40°C, 75°C, and 110°C, and the resistance value at 40°C was used as R0 to calculate the TCR. The composition ratio of Si and Cr in the sample for composition analysis in Example 1 was measured using the fundamental parameter method (FP method) with X-ray fluorescence (XRF).

[0040] The graph in Figure 2(a) shows the dependency of resistivity on N2 flow rates from 3.0 sccm to 5.5 sccm for the thin-film resistor formed in Comparative Example 1, and it can be seen that resistivity tends to increase as the N2 flow rate increases. The graph in Figure 2(b) is a partially enlarged view of the N2 flow rate range from 3.8 sccm to 4.2 sccm. Figure 2(b) shows the controllability of resistivity when the N2 gas flow rate is changed in 0.1 sccm increments, which is the resolution of the mass flow controller controlling the N2 gas flow rate. The rate of change in resistivity per resolution in this range is 20.2%. The rate of change in resistivity per resolution is the normalized value obtained by dividing the difference between the resistivity at the lower limit of the measurement range, 3.8 sccm N2 flow rate, and the resistivity at the upper limit, 4.2 sccm N2 flow rate, in the graph of Figure 2(b), by 4 (dimensionless), which is the value obtained by dividing the width between the upper and lower limits, 0.4 sccm, by the N2 flow rate resolution, 0.1 sccm, and then by the resistivity at the median, 4.0 sccm N2 flow rate.

[0041] The graph in Figure 3(a) shows the dependence of TCR on N2 flow rates from 3.0 sccm to 5.5 sccm for the thin-film resistor formed in Comparative Example 1. It can be seen that the TCR tends to become increasingly negative as the N2 flow rate increases. The graph in Figure 3(b) is a partially enlarged view of the N2 flow rate range from 3.8 sccm to 4.2 sccm, showing the controllability of the TCR when the N2 gas flow rate is changed in 0.1 sccm increments, which is the resolution of the mass flow controller controlling the N2 gas flow rate. The TCR change rate per resolution in this range is 19.5%. The TCR change rate per resolution is calculated by dividing the difference between the TCR at the lower limit of the measurement range (3.8 sccm) and the TCR at the upper limit (4.2 sccm) of the measurement range in Figure 3(b) by 4 (a dimensionless value obtained by dividing the 0.4 sccm difference between the upper and lower limits by the N2 flow rate resolution (0.1 sccm), and then by the TCR at the median N2 flow rate of 4.0 sccm.

[0042] The graph in Figure 4(a) shows the dependence of resistivity on pulse ON times from 10 μsec to 100 μsec for the thin-film resistor formed in Example 1, with an N2 flow rate of 4.1 sccm and a pulse period of 100 μsec. It can be seen that resistivity tends to increase as the pulse ON time increases. The graph in Figure 4(b) is a partial enlargement of the pulse ON time range from 48 μsec to 52 μsec, showing the controllability of resistivity when the pulse ON time is varied in 1 μsec increments, which is the time resolution of the pulsing unit 32 that controls the pulse. The rate of change in resistivity per resolution in this range is 2.7%. The rate of change in resistivity per resolution is calculated by dividing the difference between the resistivity at the lower limit of the measurement range (48 μsec) and the upper limit (52 μsec) by 4 (a dimensionless value obtained by dividing the upper and lower limits (4 μsec) by the pulse ON time resolution of 1 μsec), and then by the resistivity at the median pulse ON time of 50 μsec.

[0043] The graph in Figure 5(a) shows the dependence of resistivity on pulse ON times from 10 μsec to 100 μsec for the thin-film resistor formed in Example 1. It can be seen that as the pulse ON time increases, the TCR tends to become increasingly negative. The graph in Figure 5(b) is an enlarged view of the pulse ON time range from 48 μsec to 52 μsec, showing the controllability of the TCR when the pulse ON time is varied in 1 μsec increments, which is the time resolution of the pulsing unit 32 that controls the pulse. The TCR change rate per resolution in this range is 0.5%. The TCR change rate per resolution is calculated by dividing the difference between the TCR at the lower limit of the measurement range (48 μsec) and the TCR at the upper limit (52 μsec) by 4 (a dimensionless value obtained by dividing the upper and lower limit values ​​(4 μsec) by the pulse ON time resolution of 1 μsec), and then by the TCR at the median pulse ON time of 50 μsec.

[0044] FIG. 6 is a graph showing the relationship between the pulse ON time and the Si composition ratio in the CrSi alloy in the sputtering method according to Example 1. As shown in FIG. 6, it can be seen that the Si ratio (Si / (Si+Cr)) tends to decrease as the pulse ON time increases. Within this range, the rate of change in the Si ratio is −0.016% / μsec. While the effect is small at a pulse ON time resolution of about 1 μsec, when the pulse ON time is changed from 10 μsec to 70 μsec, it is possible to fine-tune the Si ratio in a range of Δ1.1%.

[0045] These findings indicate that in this pulse sputtering apparatus 10, the electrical properties of resistivity and TCR can be more precisely controlled by controlling the pulse ON time rather than by controlling the N2 gas flow rate. In other words, the pulse ON time has a high resolution for controlling resistivity and TCR. This makes it possible to precisely adjust the pulse ON time and pulse OFF time for film formation, enabling the formation of more accurate thermistors and resistance devices.

[0046] Furthermore, even if the alloy composition of the target material 7 deviates within a range of less than 1% due to manufacturing variations or the like, this can be accommodated by changing the pulse ON time conditions. If you want to make the TCR zero in a resistive device, etc., you can adjust the TCR by performing heat treatment at a specified temperature and time, taking advantage of the fact that the TCR changes from negative to positive when the film is heat-treated at a temperature of 300°C to 600°C for a treatment time of approximately 1 to 5 hours after deposition.

[0047] (Embodiment 2) Next, the configuration of a sputtering apparatus 10a according to the second embodiment will be described mainly with reference to FIG. 7 is a schematic cross-sectional view showing the configuration of a sputtering apparatus 10a according to embodiment 2. In FIG. 7, parts that are the same as or correspond to parts shown in FIG. 1 are given the same reference numerals, and some explanations will be omitted. 7, a viewport 50 for observing the plasma emission from outside the vacuum chamber, a spectroscope 51 for observing the spectrum of the plasma emission, and an emission spectrum calculator 52 for calculating the plasma component ratio from the emission spectrum are arranged on the side wall of the vacuum chamber 1. This sputtering apparatus 10a differs from the sputtering apparatus of embodiment 1 in that the emission spectrum calculator 52 is connected to the pulse controller 41, and the pulse conditions can be feedback-controlled based on the obtained plasma component ratio.

[0048] <Measurement of plasma emission spectrum> Measurement of the plasma emission spectrum will now be described. The emission intensity of the pulsed plasma generated in the vacuum chamber 1 fluctuates over a period of approximately 50 μsec to 1 msec, which can be set by the pulsing unit 32. Furthermore, if the magnet 11 and yoke 12 are moved by the magnet rotation mechanism 20 to move the erosion position for efficient material utilization, the spatial position of the plasma will move, and the emission intensity of the plasma detected through the viewport 50 will also fluctuate. The rotation period of the magnet 11 is approximately 0.1 sec to 10 sec. Therefore, the integration time for measurement with the spectrometer 51 must be set to at least longer than the fluctuation period of the pulsed plasma. Furthermore, it is desirable to match the rotation period of the magnet 11; alternatively, the time fluctuation of the emission intensity due to the rotation of the magnet 11 may be observed and measured at the timing when it reaches its maximum value.

[0049] <Calculation of emission intensity ratio> The calculation of the plasma emission intensity ratio will be explained using an example of an emission spectrum. The emission spectrum in FIG. 8(a) is obtained by using Cr as the target material 7. 30 Si 70 The results are obtained by measuring the plasma emission using an alloy under the conditions of an Ar flow rate of 16 sccm, an N2 flow rate of 4 sccm, a pulse ON time of 100 μsec, and a pulse OFF time of 100 μsec with a spectroscope 51 at an exposure time of 1 msec. As shown in Figure 8(a), the plasma emission spectrum has many emission peaks. These emission peaks are generated by gas particles such as Ar (Figure 8(e)) and N2 (Figure 8(d)), and sputtered particles such as Cr (Figure 8(c)) and Si (Figure 8(b)), which are excited by collisions with charged particles such as electrons that make up the plasma and emit light. In other words, the emission peaks have multiple wavelength peaks corresponding to the energy levels specific to each atom or molecule. Therefore, peaks are selected that have relatively strong emission peaks and that do not overlap and can be distinguished from each other. For example, 288.2 nm is selected for Si, 357.8 nm for Cr ions, 391.4 nm for N2 molecular ions, and 811.4 nm for Ar ions. (A) First, the counts at each peak position are tallied, and the other peaks Si, Cr, and N2 are divided by the Ar count to obtain the current emission intensity values ​​I1(Si), I1(Cr), and I1(N2), respectively. (B) Next, let Ir1(N2) = I1(N2) / (I1(Si) + I1(Cr) + I1(N2)) be the emission intensity ratio of N2. Also, let Ir1(Si) = I1(Si) / (I1(Si) + I1(Cr)) be the emission intensity ratio of Si and Cr. (C) Next, the normalized N2 emission intensity ratio Ir0(N2) is calculated by dividing the N2 emission intensity ratio Ir0(N2) and the Si and Cr emission intensity ratio Ir0(Si) in the plasma state, which are the reference values ​​recorded in advance. N2 = Ir1(N2) / Ir0(N2), normalized Si and Cr emission intensity ratio I Si =Ir1(Si) / Ir0(Si).

[0050] Example 2 In Example 2, a nitride thin film was formed under the following film formation conditions using the sputtering apparatus according to the second embodiment. -4The deposition conditions were as follows: 1.5 Pa or less, deposition pressure 0.45 Pa, power of DC power supply 30 100 W, Ar gas flow rate 15 sccm, and nitrogen gas flow rate 4.1 sccm. The pulse period (= pulse ON time + pulse OFF time) was set to 201 μsec, and plasma discharge was initiated with a pulse ON time of 97 μsec for the first deposition. Based on the data observed by spectrometer 51, the N2 emission intensity ratio calculated by emission spectrum calculator 52 was recorded as reference data, and deposition was then performed. For the next deposition, the pulse period (= pulse ON time + pulse OFF time) was set to 201 μsec, and the pulse ON time was varied in 1 μsec increments, the minimum resolution of the pulse controller, around the previous setting of 97 μsec. The pulse ON time was set to the value that minimized the difference with the recorded N2 emission intensity ratio. Overall, three deposition experiments were performed.

[0051] (Comparative Example 2) In Comparative Example 2, a nitride thin film was deposited using the sputtering apparatus configuration of Embodiment 2, but with the following modified deposition conditions from Example 2. The deposition conditions were fixed at an ultimate vacuum of 1×10 Pa or less, a deposition pressure of 0.45 Pa, a power of 100 W from DC power supply 30, an Ar gas flow rate of 15 sccm, and a nitrogen gas flow rate of 4.1 sccm. Furthermore, the deposition experiment was performed twice under the conditions where the pulse period (= pulse ON time + pulse OFF time) was fixed at 201 μsec and the pulse ON time was fixed at 100 μsec, i.e., without feedback of the plasma emission intensity ratio to the pulse conditions.

[0052] 9 shows the results of the plasma emission intensity ratio, resistivity, and TCR for Example 2 and Comparative Example 2, which were formed under the above conditions. The resistivity and TCR were evaluated in the same manner as in Example 1.

[0053] In Example 2, the pulse conditions were finely adjusted to minimize the difference from the reference value of the N2 emission intensity ratio. As a result, the change in the N2 emission intensity ratio was Δ0.5%, and the change in the Si emission intensity ratio was Δ0.3%. As a result, it can be seen that the change in resistivity was suppressed to Δ0.9%, and the change in TCR was suppressed to Δ0.1%.

[0054] In Comparative Example 2, the film was formed under fixed film formation conditions, and as a result, the change in the N2 emission intensity ratio was Δ3.9%, and the change in the Si emission intensity ratio was Δ0.3%, resulting in a change in the resistivity of Δ7.4% and a change in the TCR of Δ3.5%.

[0055] As a result, in the pulse sputtering apparatus 10a, changes in the emission intensity ratio are minimized, and as a result, fluctuations in resistivity and TCR can be suppressed, making it possible to stably deposit high-quality films over a long period of time.

[0056] Example 3 10A is a graph showing the relationship between the N2 gas flow rate and TCR in the sputtering method according to Example 3, where the pulse-ON time is controlled from minimum to maximum, and FIG. 10B is a graph showing the relationship between the N2 gas flow rate and resistivity in the sputtering method according to Example 3, where the pulse-ON time is controlled from minimum to maximum.

[0057] Figures 10A and 10B are graphs summarizing the trends in TCR and resistivity for a given target material composition, depending on the pulse-on time and N2 gas flow rate. By creating such graphs, or data tables, it is possible to precisely set the conditions for film deposition to achieve target TCR and resistivity values. In Figures 10A and 10B, the horizontal axis represents the N2 gas flow rate. Because the gas flow rate resolution is large and coarse, the graphs are stepped. The three plots, ●▲■, represent differences in pulse-on time. Because the resolution of the pulse-on time can be precisely set, it can actually be set to more than 50 steps, not just three. In other words, even under the same gas flow rate conditions, varying the pulse-on time can finely change the resistivity and TCR.

[0058] (Adjustment example 1) For example, consider a case where the TCR is adjusted to a target value as adjustment example 1. As shown in Fig. 10A, it can be seen that the TCR tends to change to the negative side as the N2 gas flow rate increases, and to the positive side as the pulse ON time decreases. Therefore, for example, the N2 gas flow rate is set so that the TCR is below the target value, and the pulse ON time is changed in a decreasing direction from the maximum value, and the pulse ON time is set so that the difference from the target value is minimized.

[0059] It is also possible to change the duty ratio of the pulse ON instead of changing the pulse ON time alone. Duty ratio = ON time / (ON time + OFF time), and the tendency to change is the same. When changing the duty ratio, the pulse frequency is constant, which may improve the stability of the plasma discharge. As shown in the graph in Figure 10B, the resistivity has a tendency of being opposite to that of the TCR. The adjustment direction can also be changed in the opposite direction, so the explanation will be omitted.

[0060] Example 4 Fig. 11A is a graph showing the relationship between the pulse-ON time and the N2 emission intensity ratio when the N2 gas flow rate is changed in the sputtering method according to Example 4. Fig. 11B is a graph showing the relationship between the pulse-ON time and the Si emission intensity ratio when the N2 gas flow rate is changed in the sputtering method according to Example 4.

[0061] 11A and 11B are graphs summarizing the results of the N emission ratio and the Si emission ratio for a certain Cr—Si target composition, with respect to the pulse ON time condition and the N 2 gas flow rate condition. The rate of change of the N emission ratio with respect to the pulse ON time is 0.31% / μsec, and the rate of change with respect to the N2 flow rate is about 2% per 0.1 sccm. On the other hand, the rate of change of the Si emission ratio with respect to the pulse ON time is -0.04% / μsec, and changes with respect to the N2 flow rate do not need to be taken into consideration at all within the range of this graph. By having a graph like this, or in other words, a data table, it is possible to see how the pulse conditions can be changed to control the composition ratio in response to changes in the emission ratio.

[0062] (Adjustment example 2) For example, as Adjustment Example 2, a case where the composition ratio is adjusted to a constant value, for example, a case where the N ratio is adjusted when it is deviated, will be described. The pulse ON time is changed so that the composition ratio obtained from the plasma emission remains constant. Specifically, as shown in Figure 11A, when the N ratio is low, the pulse ON time is adjusted to be longer, as indicated by the arrow pointing to the upper right, and when the N ratio is high, the pulse ON time is adjusted to be shorter, as indicated by the arrow pointing to the lower left. Note that changing the pulse ON time will also change the Si ratio, but as shown in Figure 11B, the rate of change in the Si ratio is about one-tenth of the rate of change in the N ratio, so adjusting the pulse ON time by about 5 μsec has little effect, and the change in the Si ratio is not a problem.

[0063] (Adjustment example 3) For example, as Adjustment Example 3, a case where the composition ratio is adjusted to a constant value, for example, a case where the Si ratio is adjusted when it deviates, will be described. As shown in Figure 11B, when the Si ratio is low, the pulse ON time is shortened as indicated by the arrow pointing to the upper left, and when the Si ratio is high, the pulse ON time is lengthened as indicated by the arrow pointing to the lower right. Note that when the pulse ON time is changed by 5 μsec or more, the change in the N ratio cannot be ignored, so the N2 flow rate is also changed by about 0.1 sccm to cancel out the change in the N ratio. In other words, when the pulse ON time is shortened, the N2 flow rate is increased by about 0.1 sccm, and when the pulse ON time is lengthened, the N2 flow rate is decreased by about 0.1 sccm. As described above, even if the composition varies depending on the lot of the target material, or even if the target material is worn out after a long period of film formation, the gas flow rate and pulse conditions can be changed based on the state of the target material from the plasma emission spectrum. This minimizes variations in electrical properties, making it possible to stably form, for example, nitride resistive thin films.

[0064] In addition, the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example. [Industrial Applicability]

[0065] The sputtering apparatus and sputtering method according to the present invention are useful for the stable formation of nitride thin film devices such as high-precision resistors with high resistance and zero TCR, and high-precision thermistors with large TCR and high sensitivity. [Explanation of symbols]

[0066] 1. Vacuum chamber 2 pumps 3. Gate valve 4 Gas supply source 5 PCB holder 6 PCB 7 Target material 8 Backing Plate 10, 10a Sputtering equipment 11 Magnet 12 York 20. Magnet rotation mechanism 30 DC power supply 32 Pulsing Unit 40 Power supply controller 41 Pulse Controller 50 viewports 51 Spectrometer 52 Emission spectrum calculator

Claims

1. a vacuum chamber in which a target material and a substrate can be placed facing each other; a DC power source electrically connectable to the target material; a gas supply source that introduces a film forming gas containing nitrogen gas into the vacuum chamber; a pulsing unit for pulsing the current flowing from the DC power supply to the target material; a viewport for observing plasma generated in the vacuum chamber; a spectrometer for detecting an emission spectrum of the plasma; an emission spectrum calculator that calculates an emission intensity ratio between the target material and a deposition gas containing nitrogen gas from the position and intensity of the characteristic peak of the detected emission spectrum; a pulse controller that sets pulse ON / OFF times in the pulsing unit based on the calculated emission intensity ratio of the deposition gas; Equipped with generating plasma in the vacuum chamber using a sintered alloy target material having a composition of two or more elements including Si and Cr as the target material; the emission spectrum calculator normalizes the measured emission intensity of the current value of the emission peak of the plasma to an emission intensity value of the plasma state that is a pre-recorded reference value, the pulse controller calculates a current value of the nitrogen emission intensity ratio in the entire film forming gas, and feedback-controls a pulse ON time so that the nitrogen emission intensity ratio minimizes a difference between the reference value and the current value; and a nitrogen gas flow rate is increased by 0.1 sccm when the pulse-ON time is changed to be longer by 5 μsec or more, and a nitrogen gas flow rate is increased by 0.1 sccm when the pulse-ON time is changed to be shorter by 5 μsec or more, thereby forming a nitride thin film having a ternary or higher composition containing Si, Cr, and nitrogen on the substrate.

2. A sputtering method using the sputtering apparatus according to claim 1, setting pulse ON / OFF times in the pulsing unit to change the composition ratio of two or more metals contained in the nitride thin film; Sputtering method.

3. A sputtering method using the sputtering apparatus according to claim 1, measuring the plasma generated in the vacuum chamber with the spectrometer; a step of normalizing the measured current value of the emission intensity of the plasma emission peak with the value of the emission intensity in the plasma state, which is a pre-recorded reference value; calculating a current value of the nitrogen emission intensity ratio in the entire film forming gas; feedback-controlling the pulse ON time so that the difference between the reference value and the current value of the nitrogen emission intensity ratio is minimized; when a difference between the current value of the Si emission intensity ratio to the total emission intensity ratio of Si and Cr and the reference value is greater than a predetermined range, feedback-controlling the pulse-ON time so that the current value of the Si emission intensity ratio to the total emission intensity ratio of Si and Cr approaches the reference value, and when the pulse-ON time is changed to be longer by 5 μsec or more, decreasing the nitrogen gas flow rate by 0.1 sccm, and when the pulse-ON time is changed to be shorter by 5 μsec or more, increasing the nitrogen gas flow rate by 0.1 sccm; A sputtering method comprising:

4. preparing a vacuum chamber in which a target material having a binary or more composition containing Si and Cr and a substrate can be disposed facing each other; electrically connecting to the target material; introducing a film forming gas containing nitrogen gas into the vacuum chamber; detecting an emission spectrum of plasma generated in the vacuum chamber; calculating an emission intensity ratio between the target material and a deposition gas containing nitrogen gas from the position and intensity of the characteristic peak of the detected emission spectrum; a step of setting pulse ON / OFF times based on the calculated emission intensity ratio of the deposition gas to pulse the current flowing through the target material; Including, In the step of calculating the emission intensity ratio of the film forming gas, the present value of the emission intensity of nitrogen is normalized with the value of the emission intensity of nitrogen in a plasma state, which is a previously recorded reference value, for the present value of the emission intensity of the characteristic peak of nitrogen in the detected emission spectrum, and the present value of the emission intensity of nitrogen is calculated; feedback-controlling the pulse ON time so that the difference between the reference value and the current value of the nitrogen emission intensity ratio in the entire film formation gas is minimized; when a difference between the current value of the Si emission intensity ratio to the total emission intensity ratio of Si and Cr and the reference value is greater than a predetermined range, feedback-controlling the pulse-ON time so that the current value of the Si emission intensity ratio to the total emission intensity ratio of Si and Cr approaches the reference value, and when the pulse-ON time is changed to be longer by 5 μsec or more, decreasing the nitrogen gas flow rate by 0.1 sccm, and when the pulse-ON time is changed to be shorter by 5 μsec or more, increasing the nitrogen gas flow rate by 0.1 sccm; The sputtering method further comprises:

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