JP2011138994A - Method for manufacturing resistor for audio - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a resistor for audio which has stable element composition profiles of N, O, Ta, stably contains N in a resistor film, can obtain a TaN film contains less O and has substantial stoichiometry-composition, and is superior in oxidation resistance and reliability. <P>SOLUTION: An insulating film is formed on a substrate, and a resistance film containing the TaN film is formed in a pattern on the insulating film. An interlayer dielectric is formed on the resistance film, and then, the resistance film is annealed at 750-1,100°C. After that, an electrode for drawing resistance which is connected to the resistance film is formed on the interlayer dielectric. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a TaN resistance film in which elements such as N (nitrogen) and Ta (tantalum) are uniformly dispersed, there is little mixed O (oxygen), a close stoichiometric composition, and a stable composition profile is obtained. It is related with the manufacturing method of the audio resistor which is excellent in the audio characteristic consisting of

  In acoustic products such as amplifiers, it is well known that the performance of resistors used in the circuit of the output stage has an influence on sound quality. Conventionally, a polysilicon thin film resistor is used in the semiconductor integrated circuit at the output stage of the amplifier. The performance of the resistor that affects the sound quality includes a TCR value. That is, the TCR value is a temperature coefficient of resistance value, and is a characteristic indicating how much the resistance value changes due to temperature change. The smaller the TCR value (closer to 0), the more the resistance value is the temperature. High sound quality can be obtained without fluctuation. The conventional polysilicon resistor has a TCR value of about ± 100 ppm / ° C in a temperature range of about 25 to 125 ° C., and further reduces the TCR value to about ± 50 ppm / ° C. in order to further improve sound quality. Is desired.

The adjustment of the TCR value is conventionally performed by adjusting the N ₂ partial pressure ratio of the source gas when the resistance film is formed by sputtering. It has also been proposed to obtain a good TCR characteristic close to 0 as a whole by laminating a thin film resistor having a positive TCR characteristic and a thin film resistor having a negative TCR characteristic.

  As a tantalum nitride (TaN) thin film resistor for the purpose of reducing the TCR value, there is one disclosed in Patent Document 1. In this conventional tantalum nitride thin film resistor, an electrode film made of Au is formed on an upper surface of a tantalum nitride thin film through an intermediate film made of Ti, and a combined resistance temperature coefficient of the intermediate film and the electrode film is set to a first resistance. When the temperature coefficient is the temperature coefficient of resistance of the tantalum nitride thin film, the sum of the first and second temperature coefficients is −10 to 0 ppm / ° C.

JP 2004-342705 A

  However, the conventional polysilicon thin film resistor has a high film formation temperature of about 600 ° C. during film formation by low pressure CVD (Chemical Vapor Deposition), and a metal material for wiring such as Al melts. In order to avoid this, a polysilicon thin film resistor cannot be formed after these metal wirings are formed. Therefore, it is necessary to form this polysilicon thin film resistor below the metal wiring, and its formation position is restricted on a LOCOS (Local Oxidation of Silicon) oxide film. For this reason, when polysilicon is used for the thin film resistor, it is necessary to secure a space for disposing the resistor immediately above the LOCOS oxide film while avoiding the transistor region, and it is difficult to reduce the chip area.

  Further, as described above, the polysilicon thin film resistor does not necessarily have a sufficiently low TCR value. For this reason, it is difficult to obtain excellent sound quality even if a polysilicon thin film resistor is used in the semiconductor integrated circuit of the amplifier output stage.

  On the other hand, the TaN thin film resistor has a low film formation temperature of about 400 ° C. or less during film formation by sputtering. Therefore, even if the TaN thin film resistor is formed after the metal wiring is formed, the metal wiring is not melted. Does not occur. Therefore, the TaN thin film resistor can be formed on the upper layer of the metal wiring, and can be stacked on the interlayer insulating film forming the metal wiring. In particular, since the area occupancy decreases as the distance from the upper wiring layer increases, it is easy to secure a space for forming the TaN resistor, so that there is an advantage that the chip area can be reduced.

  However, since the TaN film formed by the conventional method has a low content ratio of N and a high content ratio of mixed O, there is a problem that the reliability as an audio resistor is low.

  The present invention has been made in view of such problems, and the element composition profile of N, O, and Ta is stable, N is stably contained in the resistance film, and there is little O, and the stoichiometrical nature. An object of the present invention is to provide a method for manufacturing an audio resistor having a TaN film close to the composition, excellent oxidation resistance and high reliability.

The method for manufacturing an audio resistor according to the present invention includes:
Patterning a resistive film containing at least TaN;
Annealing the resistive film at 750 to 1100 ° C .;
It is characterized by having.

Other audio resistor manufacturing method according to the present invention,
Forming an insulating film on the substrate;
Patterning a resistance film containing at least TaN on the insulating film;
Forming an interlayer insulating film on the resistance film;
Annealing the resistive film at 750 to 1100 ° C .;
Forming a resistance drawing electrode connected to the resistance film on the interlayer insulating film;
It is characterized by having.

  In this case, the annealing is preferably performed by heating the resistance film in a nitrogen gas atmosphere. The TaN film can be formed by sputtering. Further, the annealing is preferably performed after the interlayer insulating film is formed and before the electrode is formed.

  In the present invention, by annealing, the N dispersed in the upper layer and / or the lower layer at the time of forming the resistive film is diffused toward the resistive film to increase the N content ratio of the resistive film. It is.

  According to the present invention, as described above, the resistance film is annealed at 750 to 1100 ° C., so that N dispersed in the upper layer and / or lower layer is diffused toward the resistance film when the resistance film is formed. This can increase the N content of the resistive film. Thereby, the TaN film becomes close to the stoichiometric composition, the oxidation resistance of the resistance film is improved, and a highly reliable and high-quality resistor can be obtained.

It is sectional drawing which shows the resistive film which concerns on embodiment of this invention. It is a graph which shows the difference in the composition ratio of the resistor after annealing. It is a graph which shows the difference in the composition ratio of the resistor before annealing. It is sectional drawing which shows the resistive film which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a semiconductor device in which a high resistance resistance film according to an embodiment of the present invention is formed. In this semiconductor device, first, various transistors and the like are formed on a substrate 1 such as a silicon substrate. At this time, the first interlayer insulating film 10 is formed on the surface of the substrate 1, and the first wiring layer 21 is formed on the first interlayer insulating film 10 from aluminum or copper. The first wiring layer 21 is formed by forming a layer of aluminum or copper on the first interlayer insulating film 10 by a normal film forming technique, and then forming this layer into a desired wiring pattern by a patterning method using a normal resist. It is formed by patterning.

  Next, a second interlayer insulating film 11 is formed on the first interlayer insulating film 10 including these first wiring layers 21, and a second wiring layer 22 is formed on the second interlayer insulating film 11. Then, the third interlayer insulating film 12 is formed on the entire surface including the second wiring layer 22, the third wiring layer 23 is formed on the third interlayer insulating film 12, and the third interlayer including the third wiring layer 23 is formed. A fourth interlayer insulating film 13 is formed on the insulating film 12.

  The fourth interlayer insulating film 13 is formed in two layers of a lower insulating film 13a and an upper insulating film 13b. Then, after forming the lower insulating film 13a, before forming the upper insulating film 13b, a pattern is formed on the lower insulating film 13a so that the tantalum nitride (TaN) film 2 has a predetermined size and shape. The TaN film 2 can be formed as follows. That is, after forming a resist pattern (not shown) having an opening in the region where the TaN film 2 is to be formed on the lower insulating film 13a, using this resist pattern as a mask, using a Ta target, a nitrogen gas is introduced into the Ar gas. By sputtering (first sputtering) with a reaction gas added at a predetermined partial pressure ratio, TaN is deposited on the entire surface. Thereafter, the TaN film 2 can be formed by removing the resist and lifting off the TaN film 2 on the resist. Alternatively, the TaN film 2 can be formed by the following method. A TaN film is formed on the entire surface of the lower insulating film 13a by sputtering, and a resist pattern is formed on the TaN film. Then, the TaN film is etched using the resist pattern as a mask. The TaN film 2 can also be formed by this method.

  After the TaN film 2 is formed, an upper insulating film 13b is formed on the entire surface of the lower insulating film 13a including the TaN film 2, and then a fourth wiring layer 24c is formed on the fourth interlayer insulating film 13. Each wiring layer is connected by a via provided by forming a conductive material in a via hole formed in the interlayer insulating film. For example, the fourth wiring layer 24 c and the second wiring layer 22 are connected by the via 4. That is, in the step of forming the third interlayer insulating film 12 and the fourth interlayer insulating film 13, the third interlayer insulating film 12 and the fourth interlayer insulating film 13 are wet using the via holes penetrating these films and the resist film as a mask. After forming by etching or dry etching, a metal material such as aluminum is sputtered or deposited by CVD (Chemical Vapor Deposition), and this metal material is formed in the via hole, thereby forming the via 4. Then, a wiring 23 and a wiring 24 c are formed on the third interlayer insulating film 12 and the fourth interlayer insulating film 13 so as to be connected to the via 4.

  On the other hand, for the TaN film 2, after the TaN film 2 is formed, the upper insulating film 13b is formed on the entire surface of the lower insulating film 13a including the TaN film 2, and the upper insulating film 13b reaches the TaN film 2. A via hole is formed. This via hole is formed by wet etching (wet etching). In the case of wet etching, the TaN film on the bottom of the via hole due to overetching can be suppressed compared to dry etching. As a result, the processing margin is improved, and the resistance can be increased by further reducing the thickness of the TaN film 2.

  Then, a metal film such as aluminum or copper is deposited and formed in these via holes by the second sputtering to provide vias 3a and 3b.

  Thereafter, fourth wiring layers 24a and 24b are formed on the upper insulating film 13b so as to be connected to the vias 3a and 3b, respectively. By the fourth wiring layers 24a and 24b, the TaN film 2 is connected as a thin film resistor provided in a path through which an output current flows in the circuit of the output stage of the amplifier.

  Thus, in the present embodiment, after forming the upper insulating film 13b of the fourth interlayer insulating film 13, before forming the via holes for the vias 3a and 3b in the upper insulating film 13b, the device is placed in a nitrogen gas atmosphere. Then, by heating to a temperature of 750 to 1100 ° C., the TaN film 2 is annealed at a temperature of 750 to 1100 ° C. in a nitrogen gas atmosphere. This annealing can be performed by lamp annealing.

2 and 3 are graphs of measurement results in which the horizontal axis represents the sputtering time during TaN film analysis and the vertical axis represents the composition ratio of the film. FIG. 2 shows a composition ratio after annealing when the TaN film 2 is annealed, and FIG. 3 shows a composition ratio before annealing the TaN film 2. In each figure, the horizontal axis represents the sputtering time at the time of analyzing the TaN film. This shows the thickness direction of the film, and when the sputtering time is 0 minute, the analysis value of the surface of the TaN film 2 is shown. As the TaN film 2 is dug by sputtering and the sputtering time becomes longer, the analysis value of the lower part in the thickness direction of the film is shown. Therefore, each figure shows the element profile in the thickness direction of the TaN film. 2 and 3, the right end is the boundary between the lower fourth interlayer insulating film 13 and the lower insulating film 13a. Since this lower insulating film 13a is a SiO ₂ film, A Si oxide film is generated at the boundary. On the other hand, the left end of FIG. 2 and FIG. 3 is the upper surface of the film formed by sputtering. In order to pattern the TaN film into a resistive film shape, the device is taken out into the air and the resist film is patterned, The portion of the TaN film not covered with the resist film is etched, and then the resist film is removed by oxygen ashing. At this time, since the surface of the TaN film is oxidized, a Ta oxide film containing a large amount of O is formed on the surface of the TaN film.

  As shown in FIG. 3, after the TaN film is formed by sputtering, a large amount of O is present on the surface portion of the TaN film, and a TaO oxide film is formed. A relatively large amount exists. Some C (carbon) is also present on the surface of the TaN film. On the other hand, Si oxide films (Si and O) are present on the lower surface portion of the TaN film, but N is also present in a relatively large amount. Of course, a large amount of Ta and N is present in the bulk portion (the central portion in the thickness direction) of the TaN film, but a relatively large amount of O is also present. Since the conventional TaN film has such a profile of each element, N is lower than the stoichiometric composition ratio and oxygen is distributed in a relatively large amount in the bulk portion of the TaN film. For this reason, the conventional TaN film has low reliability in terms of oxidation resistance, and the audio quality is low as a resistor.

  On the other hand, in this embodiment, since the TaN film is annealed at 750 to 1100 ° C. after the formation of the interlayer insulating film (the upper insulating film 13b of the fourth interlayer insulating film 13), as shown in FIG. The profile of each element in the TaN film becomes close to the stoichiometric composition, the oxidation resistance is improved, and an excellent audio quality resistor can be obtained. That is, as shown in FIG. 2, after the TaN film is sputtered, an interlayer insulating film (upper insulating film 13b) is formed, and then annealed at 750 to 1100 ° C., so that the bulk of the TaN film containing a large amount of Ta is obtained. Thus, a film in which N diffuses toward this portion, N gathers in this bulk portion, and Ta and N are present in a ratio close to the stoichiometric composition ratio is obtained. This N is obtained by diffusion of N in the surface portion of the TaN sputtering film and N in the lower portion of the TaN sputtering film in the vicinity of the lower insulating film 13a by diffusion in the central portion (bulk portion) of the TaN sputtering film. is there. As the driving force for this diffusion, it is conceivable that entropy is high between N and Ta. Theoretically, this driving force is only an estimate, but experimentally, it is a reliable finding that N collects in the center in the thickness direction of the TaN sputtering film by high-temperature annealing. On the other hand, O present in the bulk portion of the TaN film moves mainly to the surface side of the TaN film by annealing to form an oxide layer. Since O is also supplied from the interlayer insulating film 13b on the TaN film 2, the surface oxide layer becomes thicker.

  In this way, as is clear from the comparison between FIG. 2 and FIG. 3, O decreases from the bulk portion of the central portion of the TaN film due to high temperature annealing, and O collects on the surface portion of the TaN sputtering film, The thickness of the TaO oxide film is increased. Thereby, in the bulk part of the TaN film, Ta and N are present with high purity, and the abundance ratio is very close to that of the stoichiometric amount. As a result, in order to use the TaN film in the central bulk part as a resistor of an audio amplifier, by connecting a via to the TaN film and wiring in the circuit as a resistor, high-quality audio characteristics can be obtained. can get. That is, this resistor has excellent oxidation resistance, and even if the resistor itself generates heat during the use of the audio amplifier, the resistor does not oxidize and the resistance value increases with time. There is nothing. This is because O and N in the film have moved in the direction of the diffusion driving force due to high temperature annealing, and redistribution of O and N does not occur, so the resistance value does not change even if self-heating occurs. It is believed that there is.

  In addition, this invention is not restricted to the said embodiment, A various deformation | transformation is possible. For example, the TaN film 2 is not limited to being formed in the uppermost interlayer insulating film (fourth interlayer insulating film 13) as in the above-described embodiment, but as shown in FIG. The first interlayer insulating film 10 may be formed in the lower layer. In this case, the wiring layers 24 a and 24 b connected to the TaN film 2 through the vias 3 a and 3 b are formed in the same layer as the first wiring layer 21. As described above, the interlayer insulating film on which the TaN film 2 is to be disposed is arbitrary and is not limited to the uppermost layer. However, in terms of the margin of selection of the arrangement position, the inside of the uppermost interlayer insulating film is advantageous.

  In this specification, the tantalum nitride film is expressed as a TaN film. However, it should be a TaNx film (x is a positive number), and in the present invention, Ta and N are in a one-to-one relationship. It is not limited to the existing film. In the above embodiment, after the TaN film is formed, the TaN film is annealed at a high temperature after the interlayer insulating film is formed. However, the present invention is not limited to this, and immediately after the TaN film is formed, the high temperature annealing is performed. May be. Furthermore, in the above embodiment, a via is formed in the resistor of the TaN film, and then a wiring connected to the via is formed. However, the resistor can be used for drawing out the resistance without forming the wiring. It is also possible to form only the electrode.

  In the manufacturing method of the present invention, after the TaN film is sputtered, annealing is performed at a temperature of 750 to 1100 ° C. Therefore, the N dispersed at the time of sputtering film formation diffuses near the central portion in the thickness direction of the TaN film. O gathered in the lever portion and present in the vicinity of the center of the TaN film moves mainly to the surface side of the TaN film by annealing to form an oxide layer. Since O is also supplied from the interlayer insulating film on the TaN film, the surface oxide layer becomes thicker. Due to the movement of O, Ta and N are present in the center portion of the TaN film at a ratio close to the stoichiometric composition ratio. As a result, the oxidation resistance of the TaN film becomes excellent, the resistance value variation with time is prevented, and an excellent audio quality resistor can be obtained. Therefore, the resistor of the present invention is useful as a resistor of a high quality audio amplifier.

1: silicon substrate, 2: tantalum nitride (TaN) film, 3a, 3b, 4: via, 10: first interlayer insulating film, 11: second interlayer insulating film, 12: third interlayer insulating film, 13: fourth Interlayer insulating film, 13a: lower insulating film, 13b: upper insulating film, 21: first wiring layer, 22: second wiring layer, 23: third wiring layer, 24a, 24b, 24c: fourth wiring layer

Claims (6)

Patterning a resistive film containing at least TaN;
Annealing the resistive film at 750 to 1100 ° C .;
A method of manufacturing an audio resistor, comprising: Forming an insulating film on the substrate;
Patterning a resistance film containing at least TaN on the insulating film;
Forming an interlayer insulating film on the resistance film;
Annealing the resistive film at 750 to 1100 ° C .;
Forming a resistance drawing electrode connected to the resistance film on the interlayer insulating film;
A method of manufacturing an audio resistor, comprising: 3. The method of manufacturing an audio resistor according to claim 1, wherein the annealing is performed by heating the resistance film in a nitrogen gas atmosphere. The method for manufacturing an audio resistor according to claim 1, wherein the TaN film is formed by sputtering. 3. The method of manufacturing an audio resistor according to claim 2, wherein the annealing is performed after the interlayer insulating film is formed and before the electrode is formed. 2. The N content ratio of the resistance film is increased by diffusing N dispersed in the upper layer and the lower layer when the resistance film is formed by the annealing to the resistance film. 6. A method for manufacturing an audio resistor according to any one of items 1 to 5.

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