Sputtering apparatus and sputtering method

Abstract

This invention provides a sputtering apparatus and a sputtering method. The sputtering apparatus includes: a vacuum chamber in which a target and a substrate are arranged opposite each other; a DC power supply electrically connected to the target; a gas supply source for introducing a film-forming gas containing nitrogen into the vacuum chamber; and a pulsed unit for pulsed current flowing from the DC power supply to the target. Using a sintered gold target material with a binary or higher composition as the target, plasma is generated in the vacuum chamber to form a nitride thin film with a ternary or higher composition containing nitrogen on the substrate.

Description

Technical Field

[0001] The present invention relates to a sputtering apparatus and a sputtering method for forming nitride resistive thin films on substrates such as semiconductor wafers. Background Technology

[0002] In recent years, the need for higher resistance ranges has increased in devices that form thin films on substrates and create desired patterns for resistors, thermistors, and the like. This has led to a greater demand for nitride thin film formation technologies that offer higher resistivity compared to alloy materials such as nickel-chromium alloys.

[0003] From the perspective of production speed and production stability, the formation of nitride films generally uses reactive sputtering, which involves reacting the target material as raw material with the reactive gas and depositing it.

[0004] Conventionally, there are sputtering methods that control the degree of nitriding by adjusting the flow rate of nitrogen as a reactant gas and the film-forming pressure (see, for example, Patent Document 1).

[0005] Therefore, the main reference is Figure 12 This section describes existing reactive sputtering methods. Figure 12 This is a schematic cross-sectional view of an existing reactive sputtering apparatus. The vacuum chamber 1 is depressurized by a vacuum pump 2 connected via a valve 3, and can be set to a vacuum state. A gas supply source 4 supplies nitrogen-containing gas to the vacuum chamber 1 at a certain rate. The valve 3, by varying its opening and closing rate, can control the vacuum level within the vacuum chamber 1 to the desired gas pressure. A target 7 is disposed within the vacuum chamber 1. A backplate 8 supports the target 7. A DC power supply 30 is electrically connected to the backplate 8, applying voltage to the target 7 via the backplate 8, thereby dissociating a portion of the gas within the vacuum chamber 1 and generating plasma. A substrate 6 is disposed opposite the target 7 within the vacuum chamber 1. A substrate holder 5 is disposed at the lower part of the substrate 6, supporting the substrate 6.

[0006] The target material 7 is sputtered and ejected by plasma generated within the vacuum chamber 1, reaching the substrate 6 to deposit a thin film on the target material 7. Simultaneously, the gas and plasma within the vacuum chamber are deposited on the substrate and react with a target material 7 to obtain a nitride thin film.

[0007] The proportion of nitrogen in the nitride film is related to the electrical properties of the resistive device, such as resistivity and temperature coefficient (TCR). The gas supplied from the gas supply source 4 is adjusted by adjusting the mixing ratio of nitrogen gas that reacts with the film and inert gases such as argon gas that do not react with the film, so that the electrical properties are at the desired values.

[0008] Prior art literature

[0009] Patent documents

[0010] Patent Document 1: JP Patent No. 2579470 Summary of the Invention

[0011] The sputtering apparatus according to one aspect of the present invention comprises:

[0012] A vacuum chamber allows for the placement of a target and a substrate facing each other within the chamber.

[0013] A DC power supply capable of being electrically connected to the target material;

[0014] A gas supply source introduces a film-forming gas containing nitrogen into the vacuum chamber; and

[0015] The pulse unit pulses the current flowing from the DC power supply to the target material.

[0016] Using a sintered gold target material with a binary or higher composition as the target material, plasma is generated in the vacuum cavity to form a nitride film with a ternary or higher composition containing nitrogen on the substrate.

[0017] One aspect of the sputtering method of the present invention includes:

[0018] The steps of preparing a vacuum cavity in which a target and a substrate are arranged opposite each other;

[0019] The step of electrically connecting the target material;

[0020] The step of introducing a film-forming gas containing nitrogen into the vacuum chamber;

[0021] The step of detecting the emission spectrum of the plasma generated in the vacuum cavity;

[0022] The step of calculating the luminescence intensity ratio of the film-forming gas containing the target material and nitrogen gas based on the position and intensity of the characteristic peaks of the detected emission spectrum; and

[0023] The step of pulsed current flowing to the target material by setting the pulse on / off time based on the calculated luminescence intensity ratio of the film-forming gas. Attached Figure Description

[0024] Figure 1 This is a schematic cross-sectional view showing the structure of the sputtering apparatus according to Embodiment 1.

[0025] Figure 2 (a) is a graph showing the relationship between the N2 gas flow rate ratio and resistivity in Comparative Example 1, and (b) is a magnified view of a portion of the graph in (a).

[0026] Figure 3(a) is a graph showing the relationship between the N2 gas flow rate ratio and TCR in Comparative Example 1, and (b) is a magnified view of a portion of the graph in (a).

[0027] Figure 4 (a) is a graph showing the relationship between pulse turn-on time and resistivity in the sputtering method involved in Example 1, and (b) is a magnified view of a portion of the graph in (a).

[0028] Figure 5 (a) is a graph showing the relationship between pulse turn-on time and TCR in the sputtering method involved in Example 1, and (b) is a magnified view of a portion of the graph in (a).

[0029] Figure 6 This is a graph showing the relationship between the pulse on-time and the Si composition ratio in the CrSi alloy in the sputtering method described in Example 1.

[0030] Figure 7 This is a schematic cross-sectional view showing the structure of the sputtering apparatus according to Embodiment 2.

[0031] Figure 8A This is a graph showing an example of measuring the emission spectrum of plasma in the sputtering method according to Embodiment 2.

[0032] Figure 8B This is a magnified view of the emission peak of Si and the surrounding emission spectrum.

[0033] Figure 8C This is a magnified view of the emission peak of Cr and the surrounding emission spectrum.

[0034] Figure 8D This is a magnified view of the emission peak of N2 and the surrounding emission spectrum.

[0035] Figure 8E This is a magnified view of the emission peak of Ar and the surrounding emission spectrum.

[0036] Figure 9 This is a graph showing the resistivity and TCR of the nitride film formed in Embodiment 2.

[0037] Figure 10A The graph shows the relationship between N2 gas flow rate and TCR in the sputtering method involved in Example 3, and the graph shows the case where the pulse on-time is controlled from minimum to maximum.

[0038] Figure 10B This is a graph showing the relationship between N2 gas flow rate and resistivity in the sputtering method involved in Example 3, and a graph showing the case where the pulse on-time is controlled from minimum to maximum.

[0039] Figure 11A This is a graph showing the relationship between the pulse turn-on time and the N2 luminescence intensity ratio in the sputtering method involved in Example 4, and a graph showing the changes in N2 gas flow rate.

[0040] Figure 11B This is a graph showing the relationship between the pulse on-time and the ratio of Si luminescence intensity in the sputtering method described in Example 4, and a graph showing the variation of N2 gas flow rate.

[0041] Figure 12 It is a schematic cross-sectional view showing the structure of an existing sputtering device.

[0042] -Symbol Explanation-

[0043] 1. Vacuum chamber

[0044] 2 pumps

[0045] 3. Gate valve

[0046] 4. Gas supply source

[0047] 5. Substrate holder

[0048] 6 substrate

[0049] 7. Target Material

[0050] 8 Back panel

[0051] 10, 10a Sputtering apparatus

[0052] 11 Magnets

[0053] 12 Magnetic Yoke

[0054] 20. Magnet Rotation Mechanism

[0055] 30 DC power supply

[0056] 32 pulsed units

[0057] 40 Power Controller

[0058] 41 Pulse Controller

[0059] 50 Observation Port

[0060] 51 beam splitter

[0061] 52. Luminescence Spectrum Calculator Detailed Implementation

[0062] Regarding existing reactive sputtering devices (see reference) Figure 12It is difficult to precisely control the degree of nitridation of the thin film based on the resolution limit of the mass flow controller with the set gas flow rate, and it is difficult to accurately match the resistivity and temperature coefficient (TCR) of the thin film to the desired value, making stable production difficult.

[0063] Furthermore, when forming nitride films with three or more elements that can achieve higher resistivity, such as metal A-metal Bx-nitrogen Ny with three elements, even when using a metal AB alloy as the target material 7, the resistivity and TCR vary depending on the AB ratio. That is, not only the degree of nitridation y but also the AB ratio x needs to be precisely controlled. However, if the AB ratio x of the target material 7, as the raw material, deviates during target manufacturing, the electrical properties also change. Furthermore, as the target material 7 is consumed, the AB ratio x changes, and the electrical properties also change, further complicating stable production.

[0064] The present invention addresses the aforementioned problems of existing methods and aims to provide a sputtering apparatus and sputtering method that can precisely control the composition ratio of nitride thin films and stably form films.

[0065] The sputtering apparatus involved in Method 1 includes:

[0066] A vacuum chamber allows for the placement of a target and a substrate facing each other within the chamber.

[0067] A DC power supply capable of being electrically connected to the target material;

[0068] A gas supply source introduces a film-forming gas containing nitrogen into the vacuum chamber; and

[0069] The pulse unit pulses the current flowing from the DC power supply to the target material.

[0070] Using a sintered gold target material with a binary or higher composition as the target material, plasma is generated in the vacuum cavity to form a nitride film with a ternary or higher composition containing nitrogen on the substrate.

[0071] The sputtering apparatus involved in the second method may also further include, in the first method described above, the following:

[0072] An observation port is used to observe the plasma generated within the vacuum chamber.

[0073] A spectrometer is used to detect the emission spectrum of the plasma;

[0074] A luminescence spectroscopy calculator calculates at least one of the luminescence intensity ratio of the target material and the luminescence intensity ratio of nitrogen, based on the position and intensity of the characteristic peaks of the detected luminescence spectrum; and

[0075] A pulse controller sets the pulse on / off time for the pulsed unit based on the calculated luminous intensity ratio of the at least one.

[0076] The sputtering method involved in the third method is a sputtering method using the sputtering apparatus involved in the first or second method described above.

[0077] The pulse on / off time is set for the pulse unit to change the composition ratio of binary or higher metals contained in the nitride film.

[0078] Based on the above structure, even when the composition varies depending on the batch of the target material, and the target material is consumed due to long film deposition time, the gas flow rate and pulse conditions can be changed accordingly to the target material condition based on the plasma emission spectrum. Therefore, deviations in electrical properties are minimized, and thus, for example, nitride resistive films can be stably deposited.

[0079] The sputtering method involved in the fourth method is a sputtering method utilizing the sputtering apparatus involved in the second method described above, comprising:

[0080] The step of measuring the plasma generated in the vacuum cavity using the spectrometer;

[0081] The step of standardizing the luminescence intensity of the measured luminescence peak of the plasma to a standardized luminescence intensity by using the luminescence intensity value of the plasma state as a pre-recorded reference value;

[0082] The steps of calculating the luminescence intensity ratio of nitrogen in the overall film-forming gas; and

[0083] The step of feedback control of the pulse on-time to minimize the difference between the reference value and the current value of the nitrogen luminescence intensity ratio.

[0084] The sputtering methods involved in Method 5 include:

[0085] The steps of preparing a vacuum cavity in which a target and a substrate are arranged opposite each other;

[0086] The step of electrically connecting the target material;

[0087] The step of introducing a film-forming gas containing nitrogen into the vacuum chamber;

[0088] The step of detecting the emission spectrum of the plasma generated in the vacuum cavity;

[0089] The step of calculating the luminescence intensity ratio of the film-forming gas containing the target material and nitrogen gas based on the position and intensity of the characteristic peaks of the detected emission spectrum; and

[0090] The step of pulsed current flowing to the target material by setting the pulse on / off time based on the calculated luminescence intensity ratio of the film-forming gas.

[0091] In the sputtering method described in the sixth method, in the step of calculating the luminescence intensity ratio of the film-forming gas, the luminescence intensity of the nitrogen characteristic peak of the detected luminescence spectrum is normalized using the luminescence intensity value of nitrogen in the plasma state as a pre-recorded reference value, and the normalized luminescence intensity of nitrogen is calculated.

[0092] The sputtering method may also include a step of feedback control of the pulse on-time to minimize the difference between the reference value and the current value of the nitrogen luminescence intensity ratio in the overall film-forming gas.

[0093] The sputtering apparatus and method described in this invention enable precise control of the composition of nitride films containing three or more elements by applying pulsed discharge conditions. Therefore, the resistivity and TCR can be adjusted to the desired values.

[0094] Hereinafter, with reference to the accompanying drawings, the sputtering apparatus and sputtering method according to the embodiments will be described in detail. Furthermore, substantially identical components in the drawings will be given the same reference numerals.

[0095] (Implementation Method 1)

[0096] First, the main reference Figure 1 The structure of the sputtering apparatus 10 in Embodiment 1 will be described. Figure 1 This is a schematic cross-sectional view showing the structure of the sputtering apparatus 10 according to Embodiment 1.

[0097] The sputtering apparatus 10 includes: a vacuum chamber 1, a DC power supply 30, a pulsed unit 32, and a pulse controller 41. Inside the vacuum chamber 1, a target 7 and a substrate 6 are arranged facing each other. The DC power supply 30 is electrically connected to the target 7. The pulsed unit 32 pulses the current flowing from the DC power supply 30 to the target 7. The pulse controller 41 sets the pulse on-time and pulse off-time for the pulsed unit 32.

[0098] The sputtering apparatus 10 described in Embodiment 1 allows for precise control of the composition of nitride films containing three or more elements by adjusting the pulse discharge conditions based on the pulse controller 41. Therefore, it is possible to fine-tune the resistivity and TCR to the desired values.

[0099] The following describes the structural components that constitute the sputtering apparatus 10.

[0100] <Vacuum Chamber>

[0101] Vacuum chamber 1 is depressurized to a vacuum state by venting air through vacuum pump 2 connected via valve 3.

[0102] <Gas Supply Source>

[0103] The gas supply source 4 includes a gas source such as a gas cylinder and a flow controller such as a mass flow controller, which supplies the gas required for sputtering to the vacuum chamber 1 at a certain speed. The gas supplied by the gas supply source 4 can be selected from, for example, gases that are reactive with the target material such as nitrogen and oxygen, or mixtures of reactive gases and rare gases such as argon.

[0104] <valve>

[0105] By changing its opening and closing rate, valve 3 can control the vacuum level in vacuum chamber 1 to the desired gas pressure.

[0106] <Target Material>

[0107] Figure 1 In the upper part of the vacuum chamber 1, a target material 7 is disposed. The target material 7 is a metallic material with a binary or higher composition. For example, as a high resistivity material, a combination of silicon and a transition metal can be selected. For example, as metal A of two alloys AB, silicon can be selected, and as metal B, tantalum, niobium, chromium, etc., can be selected. In addition, oxygen can also be included in the conductive range of the target material 7. This also includes trace amounts of oxygen contained in the target where the atomized powder of the raw material metal is sintered.

[0108] <Backplate>

[0109] Backplate 8 supports target material 7.

[0110] DC Power Supply

[0111] The DC power supply 30 is electrically connected to the target 7 via the pulse unit 32 and the back plate 8, and can apply voltage to the target 7.

[0112] <Pulsation Unit>

[0113] The pulse unit 32 stores the DC current generated by the DC power supply 30 in a built-in capacitor or the like, and turns it on and off using a built-in semiconductor switching element or the like, thereby enabling pulsed operation. The on / off switch can be selected and set to a digital value, and the time setting resolution can be set to, for example, 1 μs.

[0114] <Pulse Controller>

[0115] The pulse controller 41 controls the on-time and off-time of the pulse indicated to the pulse unit 32 based on the relationship between the pulse conditions for generating plasma and the electrical properties of the thin film.

[0116] <Magnets and Yokes>

[0117] Magnet 11 and yoke 12 are disposed on the back side of back plate 8, generating a magnetic field on the surface of target material 7. One or more magnets 11 are required. Alternatively, magnet 11 can be either a permanent magnet or an electromagnet. The yoke 12 is connected to one end of magnet 11, forming a magnetic circuit, which can suppress unnecessary leakage of the magnetic field to the side opposite to target material 7. Through magnet 11 and yoke 12, plasma can be concentrated at the position where the parallel magnetic field relative to the plane of target material 7 is maximized, increasing the film formation rate. This position where the plasma is concentrated is called erosion. Furthermore, if erosion is concentrated at a specific location, only a portion of target material 7 is consumed, and the material cannot be effectively utilized. Therefore, magnet rotation mechanism 20 can be used to move magnet 11 and yoke 12 parallel to the surface of target material 7, thus shifting the erosion position.

[0118] <Substrate and substrate holder>

[0119] exist Figure 1 In the lower part of the vacuum chamber 1, a substrate 6 is disposed opposite to the target material 7. A substrate holder 5 is disposed in the lower part of the substrate 6 to support the substrate 6.

[0120] (The operation of the sputtering device)

[0121] Next, the operation of the sputtering apparatus 10 according to Embodiment 1 will be explained, and the sputtering method according to Embodiment 1 will also be explained (the same applies to Embodiment 2).

[0122] (1) First, a target 7 is placed in the vacuum chamber 1, and a substrate 6 is placed roughly horizontally below the target 7.

[0123] (2) Next, the vacuum pump 2 is turned on to reduce the pressure so that the vacuum chamber 1 becomes a vacuum. After the specified 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 specified gas pressure.

[0124] (3) Next, a voltage is generated by a DC power supply 30, and the pulse unit 32 is switched on and off with a specified on time and off time to pulse it, and a pulsed voltage is applied to the target material 7 to generate plasma in the vacuum chamber 1.

[0125] (4) The target material 7 is sputtered and ejected by the pulsed plasma generated in the vacuum chamber 1, reaching the substrate 6, where a thin film containing the elements constituting the target material is deposited. Simultaneously, the gas and plasma in the vacuum chamber 1 accumulate on the substrate 6 and react with a target material. Furthermore, during the time when the applied voltage is interrupted, the gas and plasma in the vacuum chamber 1 react with the target material deposited on the substrate 6, thereby forming a dense thin film of a compound formed by the reaction of the target material and the gas.

[0126] A nitride film is deposited on substrate 6 by repeating a series of pulse film formations a predetermined number of times.

[0127] (Comparative Example 1)

[0128] In Comparative Example 1, by Figure 12 The existing structure shown, in which the DC power supply 30 is connected to the direct target 7, is used to form a nitride thin film. At this time, the film formation conditions are fixed to reach a vacuum level of 1×10⁻⁶. -4 Films were deposited on a glass substrate under the following conditions: a film-forming pressure of 0.45 Pa and a DC power supply of 100 W (30 ohms); an Ar gas flow rate of 15 sccm and a nitrogen gas flow rate varying from 3.0 sccm to 5.5 sccm. Film formation was performed by varying the flow rate from 3.8 sccm to 4.2 sccm according to the minimum resolution of each mass flow controller used, which was 0.1 sccm.

[0129] (Example 1)

[0130] In Example 1, a nitride film was formed using the structure described in Example 1. At this time, the film formation conditions were fixed at a vacuum level of 1 × 10⁻⁶. -4 Under the following conditions: Pa below 1, film formation pressure 0.45 Pa, DC power supply 30 ohms 100 W, Ar gas flow rate fixed at 15 sccm, nitrogen gas flow rate fixed at 4.1 sccm, pulse period (= pulse on-time + pulse off-time) set to 100 μsec, and the minimum resolution of the pulse controller (1 μsec) varying for each pulse on-time, a film was formed on a glass substrate for resistance measurement. Furthermore, under certain conditions, a film was formed on a sapphire substrate without Si as a sample for compositional analysis.

[0131] Figure 2 (a) is a graph showing the relationship between the N2 gas flow rate ratio and resistivity in Comparative Example 1. Figure 2 (b) is to Figure 2 A magnified partial view of a portion of the chart in (a). Figure 3 (a) is a graph showing the relationship between the N2 gas flow rate ratio and TCR in Comparative Example 1. Figure 3 (b) is to Figure 3 A magnified partial view of a portion of the chart in (a). Figure 4 (a) is a graph showing the relationship between pulse on-time and resistivity in the sputtering method described in Example 1. Figure 4 (b) is to Figure 4 A magnified partial view of a portion of the chart in (a). Figure 5 (a) is a graph showing the relationship between pulse on-time and TCR in the sputtering method according to Example 1. Figure 5 (b) is to Figure 5 A magnified partial view of a portion of the chart in (a).

[0132] In addition, the film thickness of the thin film sample was measured using a stylus-type step difference meter, and the film resistance was measured using the four-probe method, calculated as film resistance [Ω / □] × film thickness [cm] = resistivity [Ω·cm]. Furthermore, the same resistance measurement was performed while the sample was heated on a hot plate, and the slope of the resistance change relative to temperature, ΔR ÷ R0 ÷ ΔT [ppm / ℃], was calculated. The resistance measurement temperatures were set to 40℃, 75℃, and 110℃, and the resistance value at 40℃ was set as R0 to calculate TCR. Furthermore, the compositional analysis of the sample in Example 1 was performed using fluorescence X-rays (XRF) and the basic parameter method (FP method) to determine the Si to Cr composition ratio.

[0133] Figure 2 The graph in (a) shows the dependence of resistivity on N2 flow rate from 3.0 sccm to 5.5 sccm in the thin film resistive body formed in Comparative Example 1. It can be seen that the resistivity tends to increase with increasing N2 flow rate. Figure 2 The graph in (b) is a magnified view of the N2 flow rate range from 3.8 sccm to 4.2 sccm. (See graph for example.) Figure 2 As shown in (b), the resistivity controllability is illustrated by varying the resistivity according to a resolution of 0.1 sccm for each mass flow controller controlling the N2 gas flow rate. The rate of resistivity change for each resolution within this range is 20.2%. Furthermore, the rate of resistivity change per resolution is... Figure 2 In the graph (b), the resistivity of the N2 flow rate at the lower limit of the measurement range of 3.8 sccm and the resistivity of the N2 flow rate at the upper limit of the measurement range of 4.2 sccm is divided by the upper limit and the width of the lower limit of 0.4 sccm divided by the resolution of the N2 flow rate of 0.1 sccm, resulting in a value of 4 (dimensionless), and is normalized by dividing by the resistivity at the middle value of N2 flow rate of 4.0 sccm.

[0134] Figure 3The graph in (a) shows the dependence of the TCR on the N2 flow rate from 3.0 sccm to 5.5 sccm in the thin film resistive body formed in Comparative Example 1. It can be seen that the negative absolute value of TCR tends to increase with the increase of N2 flow rate. Figure 3 Graph (b) is a magnified view of the N2 flow rate range of 3.8 sccm to 4.2 sccm, showing the controllability of TCR as a function of the resolution of each mass flow controller controlling the N2 gas flow rate, which is 0.1 sccm. The rate of change of TCR at each resolution within this range is 19.5%. Furthermore, the rate of change of TCR at each resolution is... Figure 3 In the graph (b), the TCR at the lower limit of the measurement range of N2 flow rate 3.8 sccm and the upper limit of the measurement range of N2 flow rate 4.2 sccm are the values ​​obtained by dividing the upper limit value and the width of the lower limit value of 0.4 sccm by the resolution of N2 flow rate of 0.1 sccm, respectively, and then dividing by the TCR at the middle value of N2 flow rate of 4.0 sccm and normalizing the result.

[0135] Figure 4 The graph in (a) shows the dependence of resistivity on the N2 flow rate with resistivity set to 4.1 sccm and pulse period set to 100 μsec in the thin film resistive body formed in Example 1, with pulse on-time ranging from 10 μsec to 100 μsec. It can be seen that resistivity tends to increase with increasing pulse on-time. Figure 4 The graph in (b) is a partial magnified view of the pulse on-time range of 48 μsec to 52 μsec, showing the controllability of resistivity as it varies with the time resolution of the pulsed unit 32 for each control pulse, which is 1 μsec. The rate of change of resistivity at each resolution within this range is 2.7%. Furthermore, the rate of change of resistivity at each resolution is a normalized value obtained by dividing the difference between the resistivity at the lower limit of the measurement range (48 μsec pulse on-time) and the resistivity at the upper limit of the measurement range (52 μsec pulse on-time) by the upper limit and the width of the lower limit (4 μsec) divided by the pulse on-time resolution (1 μsec), and then dividing by the resistivity at the middle value (50 μsec pulse on-time).

[0136] Figure 5 The graph in (a) shows the dependence of resistivity on pulse on-time from 10 μsec to 100 μsec in the thin film resistive body formed in Example 1. It can be seen that the absolute value of TCR tends to increase as the pulse on-time increases. Figure 5The graph in (b) is an enlarged view of the pulse on-time range of 48 μsec to 52 μsec, showing the controllability of TCR as it varies with the time resolution of the pulsed unit 32 for each control pulse, which is 1 μsec. The rate of change of TCR at each resolution within this range is 0.5%. Furthermore, the rate of change of TCR at each resolution is a standardized value obtained by dividing the difference between the TCR at the lower limit of the measurement range (48 μsec pulse on-time) and the TCR at the upper limit of the measurement range (52 μsec pulse on-time) by the upper limit and the width of the lower limit (4 μsec) divided by the pulse on-time resolution (1 μsec), and then dividing by the TCR at the middle value (50 μsec pulse on-time).

[0137] Figure 6 This is a graph showing the relationship between the pulse on-time and the Si composition ratio in the CrSi alloy during the sputtering method described in Example 1. Figure 6 As shown, it can be seen that the Si ratio (Si / (Si+Cr)) tends to decrease as the pulse on-time increases. The rate of change of the Si ratio in this range is -0.016% / μsec. The effect is small at the pulse on-time resolution of 1 μsec, but when the pulse on-time varies from 10 μsec to 70 μsec, it can finely adjust the Si ratio by an amount of Δ1.1%.

[0138] Therefore, in this pulse sputtering apparatus 10, it can be seen that compared to controlling the N2 gas flow rate, controlling the pulse on-time allows for more precise control of electrical characteristics, namely resistivity and TCR. In other words, the pulse on-time provides higher resolution for controlling resistivity and TCR. Thus, by precisely adjusting the pulse on-time and pulse off-time, film deposition can be performed, enabling the formation of more precise thermistors and resistive devices.

[0139] Furthermore, even if the alloy composition of the target 7 deviates by less than 1% due to manufacturing deviations, it can be accommodated by changing the pulse turn-on time.

[0140] In addition, in resistive devices and the like, if it is desired to set the TCR to zero, after film formation, heat treatment at a temperature of 300°C to 600°C for a processing time of about 1 hour to 5 hours can change the TCR from negative to positive. Thus, the TCR can be adjusted by performing heat treatment at a specified temperature and time.

[0141] (Implementation Method 2)

[0142] Next, the main references are... Figure 7 The structure of the sputtering apparatus 10a according to Embodiment 2 will be described.

[0143] here, Figure 7 This is a schematic cross-sectional view showing the structure of the sputtering apparatus 10a according to Embodiment 2. Regarding... Figure 7 , targeting Figure 1 The same or equivalent parts are given the same symbol, and the description of some parts is omitted.

[0144] Figure 7 In this sputtering apparatus 10a, an observation port 50 for observing plasma emission from outside the vacuum cavity, a spectrometer 51 for observing the spectrum of plasma emission, and an emission spectrum calculator 52 for calculating the composition ratio of the plasma based on the emission spectrum are disposed on the side wall of the vacuum cavity 1. Compared with the sputtering apparatus of Embodiment 1, this differs in that the pulse controller 41 is connected to the emission spectrum calculator 52, and the pulse conditions are feedback-controlled based on the obtained plasma composition ratio.

[0145] Measurement of the emission spectrum of plasma

[0146] The measurement of the plasma emission spectrum is explained. The emission intensity of the pulsed plasma generated in vacuum chamber 1 varies periodically from approximately 50 μsec to 1 msec, which can be set by pulse unit 32. Furthermore, to effectively utilize the material, when the magnet 11 and yoke 12 are moved by the magnet rotation mechanism 20, causing the erosion position to shift, the spatial position of the plasma also shifts, thus the emission intensity of the plasma detected from observation port 50 also varies. The rotation period of magnet 11 is approximately 0.1 sec to 10 sec. Therefore, the cumulative time for measurement using spectrometer 51 needs to be set at least longer than the variation period of the pulsed plasma. Furthermore, it is preferable to match it with the rotation period of magnet 11, so that the temporal variation of the emission intensity based on the rotation of magnet 11 can be observed and measured at the maximum value.

[0147] <Calculation of Luminous Intensity Ratio>

[0148] The calculation of the luminescence intensity ratio of plasma is illustrated using the example of emission spectrum. Figure 8A The emission spectrum was determined by spectrometer 51 under the following conditions: exposure time 1 msec using Cr30Si70 alloy as target material 7, Ar flow rate 16 sccm, N2 flow rate 4 sccm, pulse on-time 100 μsec, and pulse off-time 100 μsec.

[0149] like Figure 8A As shown, the emission spectrum of the plasma contains multiple emission peaks. These emission peaks are Ar( Figure 8E ), N2 ( Figure 8D These gas particles, Cr ( Figure 8C), Si ( Figure 8B The emission peak is the peak emitted by the collision of sputtered particles (such as electrons) with charged particles (such as electrons) that constitute the plasma. In other words, the emission peak has multiple wavelengths corresponding to the energy levels unique to each atom and molecule. Therefore, the peak is selected under the condition of having a strong emission peak and being distinguishable because the emission peaks of individual atoms and molecules do not overlap. For example, 288.2 nm was selected for Si, 357.8 nm for Cr ions, 391.4 nm for N2 molecular ions, and 811.4 nm for Ar ions.

[0150] (A) First, accumulate the counts at each peak position, and use the count of Ar divided by the other peaks Si, Cr, and N2 as the luminous intensity of the current value, which are set as I1(Si), I1(Cr), and I1(N2), respectively.

[0151] (B) Next, let Ir1(N2)=I1(N2) / (I1(Si)+I1(Cr)+I1(N2)) be the luminous intensity ratio of N2. In addition, let Ir1(Si)=I1(Si) / (I1(Si)+I1(Cr)) be the luminous intensity ratio of Si and Cr.

[0152] (C) Next, the luminescence intensity ratios of N2 (Ir1(N2)) and Si and Cr (Ir1(Si)) are divided by the plasma state luminescence intensity ratios of N2 (Ir0(N2)) and Si and Cr (Ir0(Si)) as pre-recorded reference values, and this is set as the normalized luminescence intensity ratio of N2 (Ir0(Si)). N2 =Ir1(N2) / Ir0(N2), the normalized ratio of Si to Cr luminescence intensity I Si =Ir1(Si) / Ir0(Si).

[0153] (Example 2)

[0154] In Example 2, using the sputtering apparatus described in Example 2, a nitride film was formed under the following film-forming conditions. At this time, the film-forming conditions were fixed at a vacuum level of 1 × 10⁻⁶. -4The film formation pressure was 0.45 Pa, and the power supply was 100 W from a DC power source of 30 ohms. The Ar gas flow rate was fixed at 15 sccm, and the nitrogen gas flow rate was fixed at 4.1 sccm. Furthermore, the pulse period (= pulse on-time + pulse off-time) was set to 201 μsec. For the initial film formation, plasma discharge was initiated with a pulse on-time of 97 μsec. Based on the observation data in the spectrometer 51, the N2 luminescence intensity ratio calculated by the luminescence spectrum calculator 52 was recorded as the baseline data for film formation. For the next film formation, the pulse period (= pulse on-time + pulse off-time) was set to 201 μsec. The pulse on-time was centered on the previously set value of 97 μsec, varying according to the minimum resolution of the pulse controller (i.e., every 1 μsec) to minimize the difference between the pulse on-time and the recorded N2 luminescence intensity ratio. Film formation was then performed. Three film formation experiments were conducted in total.

[0155] (Comparative Example 2)

[0156] In Comparative Example 2, the film-forming conditions of Example 2 were modified and a nitride film was formed using the sputtering apparatus described in Embodiment 2, as follows. At this time, the film-forming conditions were fixed to achieve a vacuum degree of 1 × 10⁻⁶. -4 With a pressure below Pa, a film-forming pressure of 0.45 Pa, and a DC power supply of 100 W (30 ohms), the Ar gas flow rate was fixed at 15 sccm, and the nitrogen gas flow rate was fixed at 4.1 sccm. Furthermore, the pulse period (= pulse on-time + pulse off-time) was set to 201 μsec, and two film-forming experiments were conducted under the condition of a fixed pulse on-time of 100 μsec, i.e., without feeding back the plasma luminescence intensity ratio to the pulse conditions.

[0157] Figure 9 The figures show the plasma emission intensity ratio, resistivity, and TCR results of Example 2 and Comparative Example 2, which were formed under the above conditions. Furthermore, the evaluation methods for resistivity and TCR are the same as in Example 1.

[0158] In Example 2, the pulse conditions were finely adjusted to minimize the difference between the N2 luminescence intensity ratio and the reference value. The change in the N2 luminescence intensity ratio was Δ0.5%, and the change in the Si luminescence intensity ratio was Δ0.3%. As a result, the change in resistivity was suppressed to Δ0.9%, and the change in TCR was suppressed to Δ0.1%.

[0159] In Comparative Example 2, with the film formation conditions fixed, the change in the N2 luminescence intensity ratio was Δ3.9%, and the change in the Si luminescence intensity ratio was Δ0.3%. As a result, the resistivity changed by Δ7.4%, and the TCR changed by Δ3.5%.

[0160] Therefore, in the pulse sputtering apparatus 10a, the change in the luminescence intensity ratio is suppressed to a minimum. As a result, the variation in resistivity and TCR can be suppressed, and high-quality films can be formed stably for a long time.

[0161] (Example 3)

[0162] Figure 10A The graph shows the relationship between N2 gas flow rate and TCR in the sputtering method involved in Example 3, and the graph shows the case where the pulse on-time is controlled from minimum to maximum. Figure 10B This is a graph showing the relationship between N2 gas flow rate and resistivity in the sputtering method involved in Example 3, and a graph showing the case where the pulse on-time is controlled from minimum to maximum.

[0163] Figure 10A as well as Figure 10B This is a chart summarizing the trends in TCR and resistivity under conditions of assumed target material composition, pulse on-time, and N2 gas flow rate. Using such charts, i.e., data tables, conditions can be precisely set to achieve target TCR and resistivity values ​​for film deposition. Figure 10A as well as Figure 10B In the graph, the horizontal axis represents the N2 gas flow rate. Because the gas flow rate resolution is relatively large and coarse, the graph appears as a stepped structure. Furthermore, the three curves (●▲■) represent different pulse on-times. The pulse on-time resolution can be set with finer precision; therefore, it can actually be set to 50 steps or more, not just 3. In other words, even with the same gas flow rate, varying the pulse on-time can result in precise changes in resistivity and TCR.

[0164] (Adjustment Example 1)

[0165] For example, as adjustment example 1, consider the case where the TCR is adjusted to the target value. Figure 10A As shown, TCR tends to change towards the negative side if the N2 gas flow rate increases, and towards the positive side if the pulse on-time is reduced.

[0166] Therefore, for example, by setting the N2 gas flow rate below the TCR value, the pulse on-time can be varied in the direction of decreasing from the maximum value, and the pulse on-time with the minimum difference from the target value can be set.

[0167] Alternatively, instead of varying the pulse on-time alone, the duty cycle of the pulse can be varied. Duty cycle = on-time / (on-time + off-time), ensuring the variation tends to be consistent. When the duty cycle is varied, the pulse frequency is not constant, thus potentially improving the stability of the plasma discharge.

[0168] resistivity Figure 10B The chart shows a trend that is the opposite of TCR in terms of positive and negative values; adjusting the direction should also be done in the opposite way. Therefore, further explanation is omitted.

[0169] (Example 4)

[0170] Figure 11A The graph shows the relationship between the pulse turn-on time and the N2 luminescence intensity ratio in the sputtering method described in Example 4, and the diagram shows the variation of the N2 gas flow rate. Figure 11B The graph shows the relationship between the pulse turn-on time and the luminescence intensity ratio of Si in the sputtering method described in Example 4, and the graph shows the situation of changing the N2 gas flow rate.

[0171] Figure 11A as well as Figure 11B This is a chart summarizing the results of the N luminescence ratio and Si luminescence ratio under the conditions of pulse turn-on time and N2 gas flow rate for a certain Cr-Si target composition.

[0172] The N emission ratio changes by 0.31% / μsec with respect to the pulse on-time, and by approximately 2% per 0.1 sccm with respect to the N2 flow rate. On the other hand, the Si emission ratio changes by -0.04% / μsec with respect to the pulse on-time, and its change with the N2 flow rate is negligible within the range shown in this graph. This graph, i.e., a table containing data, demonstrates how variations in the emission ratio can control the composition ratio by altering the pulse conditions.

[0173] (Adjustment Example 2)

[0174] For example, as adjustment example 2, we will explain the case where the composition ratio is adjusted to a certain value, such as when adjusting the N ratio offset.

[0175] The pulse on-time is varied to keep the composition ratio obtained from plasma luminescence constant. Specifically, such as... Figure 11A As shown, when N is relatively low, the pulse on-time is increased as indicated by the upper right arrow; when N is relatively high, the pulse on-time is shortened as indicated by the lower left arrow. Furthermore, changing the pulse on-time also changes the Si ratio, but as... Figure 11B As shown, the rate of change of the Si ratio is about one-tenth that of the rate of change of the N ratio. Therefore, the effect of the adjustment based on the pulse on-time of about 5μsec is small, and the change of the Si ratio is not a problem.

[0176] (Adjustment Example 3)

[0177] For example, as adjustment example 3, we will explain the case where the composition ratio is adjusted to a certain value, such as when adjusting the Si ratio offset.

[0178] like Figure 11B As shown, adjustments are made to shorten the pulse on-time when the Si ratio is low (as indicated by the upper left arrow) and increase the pulse on-time when the Si ratio is high (as indicated by the lower right arrow). Furthermore, when the pulse on-time changes by more than 5 μsec, the change in the N ratio cannot be ignored; therefore, to eliminate the change in the N ratio, the N2 flow rate is also changed by approximately 0.1 sccm. In other words, shortening the pulse on-time increases the N2 flow rate by approximately 0.1 sccm, and increasing the pulse on-time reduces it by approximately 0.1 sccm.

[0179] As described above, even when the composition varies depending on the batch of the target material, and even with long film deposition and target material consumption, the gas flow rate and pulse conditions can be adjusted according to the plasma emission spectrum and the condition of the target material. Therefore, deviations in electrical properties are minimized, thus enabling, for example, the stable deposition of nitride resistive films.

[0180] Furthermore, this disclosure includes a method of appropriately combining any of the various implementation methods and / or embodiments to achieve the effects of each implementation method and / or embodiment.

[0181] Industrial availability

[0182] The sputtering apparatus and sputtering method involved in this invention are useful for the stable formation of nitride thin film devices such as high-resistance resistors with zero TCR and high-precision thermistors with large TCR and high sensitivity.

Claims

1. A sputtering method using a sputtering apparatus, the sputtering apparatus comprising: A vacuum chamber allows for the placement of a target and a substrate facing each other within the chamber. A DC power supply capable of being electrically connected to the target material; A gas supply source introduces a film-forming gas containing nitrogen into the vacuum chamber; A pulsed unit pulses the current flowing from the DC power supply to the target material; An observation port is used to observe the plasma generated within the vacuum chamber. A spectrometer is used to detect the emission spectrum of the plasma; The emission spectrum calculator calculates the emission intensity ratio of the film-forming gas containing the target material and nitrogen gas based on the position and intensity of the characteristic peaks of the detected emission spectrum. and The pulse controller, based on the calculated luminescence intensity ratio of the film-forming gas, sets the pulse on / off time for the pulsed unit. A sintered gold target material containing a binary or higher composition of Si and Cr is used as the target material to generate plasma within the vacuum cavity. The emission spectrum processor sets the emission intensity of the measured emission peak of the plasma as the emission intensity obtained by normalizing the emission intensity value of the plasma state, which is a pre-recorded reference value. In the pulse controller, the current value of the nitrogen luminescence intensity ratio in the overall film-forming gas is calculated, and the pulse on-time is controlled by feedback to minimize the difference between the reference value and the current value of the nitrogen luminescence intensity ratio. Furthermore, when the difference between the current value of the luminous intensity ratio of Si to Cr and the reference value is greater than a predetermined range, feedback control is performed on the pulse on-time to make the current value of the luminous intensity ratio of Si to Cr close to the reference value. As a result, if the pulse on-time is increased by more than 5 μs, the nitrogen flow rate is reduced by 0.1 sccm, and if the pulse on-time is shortened by more than 5 μs, the nitrogen flow rate is increased by 0.1 sccm, thereby forming a nitride film with a ternary or higher composition containing Si and nitrogen on the substrate.

2. The sputtering method according to claim 1, wherein, The pulse on / off time is set for the pulse unit to change the composition ratio of binary or higher metals contained in the nitride film.

3. The sputtering method according to claim 1, wherein, The sputtering method includes: The step of measuring the plasma generated in the vacuum cavity using the spectrometer; The step of setting the luminescence intensity of the current value of the measured luminescence peak of the plasma to the luminescence intensity obtained by normalizing the value of the luminescence intensity of the plasma state as a pre-recorded reference value; The step of calculating the current value of the luminescence intensity ratio of nitrogen in the overall film-forming gas; The step of feedback control of the pulse on-time to minimize the difference between the reference value and the current value of the nitrogen luminescence intensity ratio; and If the difference between the current value of the luminescence intensity ratio of Si to Cr and the reference value is greater than a specified range, feedback control is performed on the pulse on-time to make the current value of the luminescence intensity ratio of Si to Cr close to the reference value. This involves reducing the nitrogen flow rate by 0.1 sccm when the pulse on-time increases by more than 5 μs, and increasing the nitrogen flow rate by 0.1 sccm when the pulse on-time decreases by more than 5 μs.

4. A sputtering method, comprising: The steps of preparing a vacuum cavity capable of arranging a target material containing a binary or higher composition of Si and Cr and a substrate facing each other inside the cavity. The step of electrically connecting the target material; The step of introducing a film-forming gas containing nitrogen into the vacuum chamber; The step of detecting the emission spectrum of the plasma generated within the vacuum chamber; The step of calculating the ratio of the luminescence intensity of the film-forming gas containing the target material and nitrogen gas based on the position and intensity of the characteristic peak of the detected luminescence spectrum; and Based on the calculated luminescence intensity ratio of the film-forming gas, the step of setting the pulse on / off time to pulse the current flowing to the target material is as follows: In the step of calculating the luminescence intensity ratio of the film-forming gas, the luminescence intensity of nitrogen is calculated as the current value of the luminescence intensity of nitrogen in the plasma state, which is normalized to a pre-recorded reference value, for the current value of the characteristic peak of nitrogen in the detected luminescence spectrum. The sputtering method further includes the step of: feedback control of the pulse on-time to minimize the difference between the reference value and the current value of the nitrogen luminescence intensity ratio in the overall film-forming gas; as well as If the difference between the current value of the luminescence intensity ratio of Si to Cr and the reference value is greater than a specified range, feedback control is performed on the pulse on-time to make the current value of the luminescence intensity ratio of Si to Cr close to the reference value. This involves reducing the nitrogen flow rate by 0.1 sccm when the pulse on-time increases by more than 5 μs, and increasing the nitrogen flow rate by 0.1 sccm when the pulse on-time decreases by more than 5 μs.

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