JP2006196663A - Etching method, program, recording, computer-readable recording medium, and plasma processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control breakdown and deterioration of underlayer film on the occasion of etching a laminated insulating film, having a coated silicon-based insulating film. <P>SOLUTION: A substrate W, on which an SOG film and a TEOS film are laminated on the underlayer film of a titanium nitride film, is accommodated within a processing chamber S and is supported on a susceptor 13. The processing chamber S is maintained in the evacuated atmosphere and the etching gas, that does not contain O<SB>2</SB>gas but C<SB>4</SB>F<SB>8</SB>gas and N<SB>2</SB>gas, is introduced into the processing chamber S from an upper electrode 30. High frequency is impressed on the susceptor 13 by a high-frequency power source, and the gas in the processing chamber S is converted to plasma. Consequently, the laminated film is etched on the substrate W. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an etching method for etching a silicon-based insulating film stacked on a substrate, a program for executing the etching method, a computer-readable recording medium, and a plasma processing apparatus.

For example, in a manufacturing process of an electronic device having a multilayer wiring structure or the like, for example, silicon-based insulating films are formed in a multilayer on a base film of a substrate. Thereafter, the stacked film formed by stacking the silicon-based insulating films is etched into a predetermined shape such as a groove or a hole. Conventionally, etching of this laminated film has been performed using, for example, an etching gas containing a CF (fluorocarbon) -based reaction gas one layer at a time from the upper layer. Has been proposed (see, for example, Patent Document 1). In addition, an etching gas in which O ₂ gas is added to a CF-based reaction gas in order to remove excess carbon has been used.

  By the way, in an electronic device, as shown in FIG. 10, a plurality of Al wirings 100 shifted in the vertical direction, for example, may be formed in a multilayer wiring structure. On the upper layer of the Al wiring 100, an insulating laminated film 102 is formed with a base film 101 interposed therebetween, and a resist film R serving as an etching mask is further formed thereon. In such a case, in order to eliminate the influence of the shifted Al wiring 100 and flatten the surface of the laminated film 102, one layer of the laminated film 102 is coated and insulated by a coating method such as an SOG (Spin On Glass) film. A membrane 103 is used. The coating insulating film 103 is formed by applying and drying a liquid coating solution, and the film thickness varies depending on the location so that the upper surface is flat.

  When the laminated film 102 having the coating insulating film 103 whose film thickness varies as described above is etched by the CF-based etching gas to which oxygen gas is added as described above, the coating insulating film 103 is made of another insulating film. Since the etching rate is slower than that of the film 104, the etching time of the entire laminated film 102 is greatly influenced by the thickness of the coating insulating film 103. For this reason, the etching time of the laminated film 102 differs greatly between a place where the coating insulating film 103 is thick and a place where the coating insulating film 103 is thin. That is, the time from when etching of the surface of the laminated film 102 is started until the base film 101 is exposed varies greatly for each Al wiring 100. As a result, part of the base film 101 is exposed to the etching gas for a long time before the etching of the entire surface of the laminated film 102 is completed. For this reason, the base film 101 which is not an object to be etched is scraped, and the base film 101 may be damaged or deteriorated.

JP 2000-235773 A

  The present invention has been made in view of this point, and an object of the present invention is to suppress damage and deterioration of a base film when etching a laminated film including a silicon-based coating insulating film.

In order to achieve the above object, the present invention provides a method for etching a laminated film formed on a substrate and having a plurality of silicon-based insulating films, wherein the laminated film is formed by a coating method. An etching gas containing a silicon-based insulating film and containing a fluorocarbon-based gas and a nitrogen gas and not containing an oxygen gas is introduced into the processing chamber, and the stacked film on the substrate is etched in the processing chamber. Features. Note that the silicon-based insulating film is an insulating film containing silicon. The silicon insulating film includes a silicon oxide insulating film such as SiO ₂ , SiOF, or SiOC containing silicon and oxygen.

  By using nitrogen gas as part of the etching gas as in the present invention, the difference in etching rate between the coated silicon-based insulating film and the other silicon-based insulating films can be reduced. As a result, the etching rate of the coated silicon-based insulating film relative to other silicon-based insulating films increases relatively. For example, even if the coated silicon-based insulating film has a film thickness difference depending on the location, the etching of the laminated film is completed. Thus, the time difference in timing to reach the base film can be reduced. Therefore, a part of the base film is not exposed to the etching gas for a long time, and damage and deterioration of the base film can be suppressed. In addition, since the etching rate of the coated silicon-based insulating film and the other silicon-based insulating films are approximately the same, the etching is performed vertically and the etching shape is improved. In the coating method, a film is formed by applying a liquid coating solution on a substrate and drying it.

  The coated silicon insulating film may be an SOG film. Further, the ratio of the etching rates of the coated silicon-based insulating film and the other silicon-based insulating films may be adjusted by adjusting the amount of nitrogen gas introduced. By doing so, the laminated film can be etched into a desired shape by optimizing the etching rate ratio between the coating film and the other insulating film.

  The laminated film may include a CVD silicon-based insulating film formed by chemical vapor deposition in addition to the coated silicon-based insulating film. The CVD silicon-based insulating film may be a silicon oxide film.

  The introduction amount of the nitrogen gas may be adjusted to a flow rate of 30 to 40% of the total flow rate of the etching gas.

  The underlying film of the laminated film may be a nitrogen-based metal film. In such a case, the etching selectivity between the laminated film and the base film by the etching gas increases. Therefore, etching of the base film is further suppressed, and damage to the base film is suppressed. The nitrogen-based metal film may be titanium nitride.

  According to another aspect of the present invention, there is provided a program for causing a computer to implement the etching method according to any one of claims 1 to 8. According to another aspect of the present invention, there is provided a computer-readable recording medium on which a program for causing a computer to implement the etching method according to any one of claims 1 to 8 is recorded. Furthermore, according to another aspect of the present invention, there is provided a plasma processing apparatus having a control unit that performs the etching method according to any one of claims 1 to 8.

  According to the present invention, damage and deterioration of the underlying film during etching can be suppressed, so that the device quality can be improved.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 is an explanatory view of a longitudinal section showing an outline of a configuration of an etching apparatus 1 in which an etching method according to this embodiment is performed.

  The etching apparatus 1 has, for example, a substantially cylindrical processing container 10. A processing chamber S is formed inside the processing container 10. The processing vessel 10 is formed of, for example, an aluminum alloy, and the inner wall surface is covered with an alumina film or an yttrium oxide film.

  A cylindrical susceptor support 12 is provided at the center bottom in the processing vessel 10 with an insulating plate 11 interposed. A susceptor 13 on which the substrate W is placed is supported on the susceptor support 12. The susceptor 13 constitutes a lower electrode. The susceptor 13 is made of, for example, an aluminum alloy.

  An electrostatic chuck 14 that holds the substrate W is provided on the susceptor 13. The electrostatic chuck 14 has an electrode layer 16 connected to a DC power source 15 inside, and a DC voltage is applied from the DC power source 15 to the electrode layer 16 to generate a Coulomb force. The substrate W can be adsorbed.

  A ring-shaped refrigerant chamber 17 is formed inside the susceptor support 12. The refrigerant chamber 17 communicates with a chiller unit (not shown) installed outside the processing container 10 through pipes 17a and 17b. The coolant or cooling water is circulated and supplied to the coolant chamber 17 through the pipes 17a and 17b, and the temperature of the substrate W on the susceptor 13 can be controlled by this circulation supply.

  A gas supply line 18 that passes through the susceptor 13 and the susceptor support 12 is connected to the upper surface of the electrostatic chuck 14, and heat transfer gas such as He gas can be supplied between the substrate W and the electrostatic chuck 14.

  A high frequency power supply 20 is electrically connected to the susceptor 13 via a matching unit 19. The high frequency power supply 20 can output a high frequency voltage having a frequency of about 2 MHz to 20 MHz, for example.

  Above the susceptor 13, an upper electrode 30 facing the susceptor 13 in parallel is provided. A plasma generation space is formed between the susceptor 13 and the upper electrode 30.

  The upper electrode 30 constitutes a shower head that ejects a predetermined etching gas onto the substrate W placed on the susceptor 13. The upper electrode 30 has, for example, a disk shape, and a plurality of gas ejection holes 30 a for introducing an etching gas into the processing chamber S are formed in the upper electrode 30.

A gas supply pipe 40 communicating with the gas ejection hole 30 a of the upper electrode 30 is connected to the upper surface of the processing container 10. The gas supply pipe 40 branches in the middle and is connected to a plurality of, for example, four gas supply sources 41, 42, 43, 44. In the present embodiment, for example, the first gas supply source 41 is filled with C ₄ F ₈ gas, and the second gas supply source 42 is filled with N ₂ gas. Ar gas is sealed in the third gas supply source 43, and CO gas is sealed in the fourth gas supply source 44. A mass flow controller 45 is provided in each branch pipe leading to each gas supply source in the gas supply pipe 40. Thereby, the gases from the gas supply sources 41 to 44 can be mixed and supplied to the processing chamber S at a predetermined flow rate ratio. The flow rate control in each mass flow controller 45 is performed by a device control unit 46 described later.

  The etching apparatus 1 is provided with an apparatus control unit 46 that controls the operation of various specifications for performing an etching process such as the DC power supply 15, the high-frequency power supply 20, and the mass flow controller 45. The apparatus control unit 46 is configured by a computer, for example, and includes a recording unit 46a in which a program P for realizing an etching process is recorded as shown in FIG. 2, an arithmetic unit 46b including a CPU that executes the program P, and the like. ing. For example, as shown in FIG. 1, a user interface unit 47 including a keyboard and a display on which a process manager inputs commands to manage the etching apparatus 1 is connected to the apparatus control unit 46. For example, the program P can be installed from the interface unit 47 using a recording medium and stored in the recording unit 46a. The apparatus control unit 46 can control the operation of the etching apparatus 1 such as the mass flow controller 45 according to the program P, and can realize a predetermined etching process.

  An exhaust pipe 50 leading to an exhaust device such as a vacuum pump (not shown) is connected to the side of the bottom of the processing container 10. By exhausting from the exhaust pipe 50, the inside of the processing chamber S can be set to a desired pressure.

  A horizontal magnetic field forming magnet 60 is provided around the processing container 10. By forming a magnetic field in the processing chamber S by the horizontal magnetic field forming magnet 60, the plasma generated in the processing chamber S can be densified and the etching efficiency can be improved.

Next, the etching process of the substrate W performed using the above etching apparatus 1 will be described. On the substrate W, for example, as shown in FIG. 3, a titanium nitride film 80 as a base film, a TEOS (tetraethoxysilane) film 81 as a CVD silicon-based insulating film, an SOG film 82 as a coated silicon-based insulating film, CVD A TEOS film 83 as an insulating film and a resist film R exposed to a predetermined pattern are stacked in order from the bottom. The TEOS films 81 and 83 are SiO ₂ films (silicon oxide films) formed by CVD using TEOS as a raw material. The TEOS film 81, the SOG film 82, and the TEOS film 83 form a stacked film 84. In this etching process, the laminated film 84 is removed from the upper surface in a concave shape, and a groove (trench) is formed in the laminated film 84.

First, the substrate W is sucked and held on the susceptor 13. The substrate W is adjusted to a predetermined temperature on the susceptor 13. Subsequently, the inside of the processing chamber S is adjusted to a predetermined pressure by the exhaust from the exhaust pipe 50. From the upper electrode 30, for example, an etching gas composed of C ₄ F ₈ gas, N ₂ gas, Ar gas, and CO gas is supplied into the processing chamber S. For example, the N ₂ gas is supplied so as to have a flow rate ratio of 30% to 40% of the total flow rate of the etching gas. A high frequency power is applied to the susceptor 13 by the high frequency power supply 20, and the gas in the processing chamber S is turned into plasma. In the processing chamber S, a magnetic field is formed by the horizontal magnetic field forming magnet 60, and the plasma is densified. Due to the action of the plasma, as shown in FIG. 4, the laminated film 84 on the substrate W is etched in a concave shape from the upper surface downward to form a groove.

Next, as in the etching process described above, the SOG film 82 and the TEOS when the laminated film 84 having the SOG film 82 and the TEOS films 81 and 83 is etched with an etching gas containing C ₄ F ₈ gas and N ₂ gas. The etching rate of the films 81 and 83 will be verified.

FIG. 5 is experimental data showing the relationship between the flow rate ratio of the N ₂ gas to the total flow rate of the etching gas and the etching rates of the SOG film 82 and the TEOS films 81 and 83. This experiment was performed under the conditions of processing pressure: 3.99 Pa (30 mT), high frequency power: 1300 W, flow rate of C ₄ F ₈ / CO / Ar: 12/50/200 cm ³ / min, substrate temperature: 20 ° C. It was broken. According to FIG. 5, the etching rate of SOG film 82 and TEOS film 81 and 83 is varied in accordance with the flow ratio of _{N 2} gas flow rate ratio of _{N 2} gas of 30% to 40%, the SOG film 82 It can be confirmed that the etching rate of the TEOS films 81 and 83 approaches. For example, when the flow rate ratio of N ₂ gas is 30% to 40%, the etching rate ratio (SOG film / TEOS film) between the SOG film 82 and the TEOS films 81 and 83 is 0.6 to 0.8 or more. . Thus, by adjusting the flow rate ratio of N ₂ gas, the etching rates of the SOG film 82 and the TEOS films 81 and 83 can be made closer, and as a result, the etching shape can be improved. For example, as shown in FIG. 6, a plurality of Al wirings 90 having different heights are formed, and a TEOS film 81 and a thickness of each of the Al wirings 90 are formed on each Al wiring 90 via a titanium nitride film 80 as a base film. Even when different SOG films 82 and TEOS films 83 are formed in order from the bottom, the etching in the SOG film 82 proceeds at the same speed as the TEOS film 81, so that the etching is performed on the stacked film 84. The difference in etching time T from the surface to the titanium nitride film 80 of each Al wiring 90 is reduced. As a result, a part of the titanium nitride film 80 is not exposed to the etching gas for a long time, and damage and deterioration of the titanium nitride film 80 are suppressed. Note that the multilayer structure in FIG. 6 is for explanation and is different from the actual scale.

Further, as shown in FIG. 7, it can be confirmed that the etching selectivity of the laminated film 84 with respect to the resist film R is improved by increasing the flow rate ratio of the N ₂ gas, and the film loss of the resist film R can be suppressed.

Next, the etching selectivity between the laminated film 84 and the titanium nitride film 80 when N ₂ gas is added to the etching gas as in the above-described etching process is verified. FIG. 8 shows an etching state when O ₂ gas is added to the etching gas and an etching state when N ₂ gas is added to the etching gas. FIG. 9 shows the etching selectivity with respect to the titanium nitride film obtained when the O ₂ gas is added and N ₂ gas is added (etching speed of the laminated film / etching speed of the titanium nitride) obtained from the etching result of FIG. It is a table | surface which shows. In this experiment, treatment pressure: 3.99 Pa (30 mT), high frequency power: 1300 W, flow rate of C ₄ F ₈ / CO / Ar / O ₂ : 10/100/200/9 cm ³ / min, C ₄ F ₈ / CO / Ar / N ₂ flow rate: 12/50/200/60 cm ³ / min, substrate temperature: 20 ° C. As shown in FIG. 9, it can be confirmed that the etching selectivity of the laminated film to the titanium nitride film is significantly higher when N ₂ gas is added than when O ₂ gas is added. Therefore, by adding N ₂ gas instead of O ₂ gas to the etching gas, it is possible to suppress the scraping of the titanium nitride film 80 during etching. Further, as shown in FIG. 8, when N ₂ gas is added, there is less bowing phenomenon in which the width of the lower portion is widened, and the etching shape is improved than when O ₂ gas is added.

The example of the embodiment of the present invention has been described above, but the present invention is not limited to this example and can take various forms. For example, in the above embodiment, the laminated film 84 is a three-layer film in which the TEOS film 81, the SOG film 82, and the TEOS film 83 are laminated in order from the bottom, but the present invention includes at least one SOG film. The present invention can also be applied to etching a laminated film having the number of layers. Further, the SOG film 82 of the laminated film 84 may be another coated silicon insulating film, for example, a Low-k film (low dielectric constant film) such as SiLK (registered trademark of Dow Chemical Co.) or HSQ film. Further, the TEOS films 81 and 83 of the laminated film 84 may be other CVD films such as HTO, BPSG, BSG, PSG, or Low-k films such as SiOC and SiOF. Furthermore, the silicon-based insulating film other than the SOG film 82 may be formed by a film forming method other than the CVD film, such as a sputtering method or a thermal oxidation method. The underlying titanium nitride film 80 may be another nitrogen-based metal film such as a TaN film. In addition, the fluorocarbon gas supplied as a reaction gas is not limited to C ₄ F ₈ , but other fluorocarbons such as CF ₄ , CHF ₃ , C ₂ F ₆ , and CH ₂ F ₂ depending on the etching material. It may be a system gas. The present invention can also be applied to etching of substrates such as semiconductor wafers, FPDs (flat panel displays), and mask reticles for photomasks.

  The present invention is useful when etching a multilayer insulating film including a coated silicon-based insulating film.

It is a longitudinal cross-sectional view explaining the outline of a structure of an etching apparatus. It is a block diagram which shows the structure of an apparatus control part. It is a longitudinal cross-sectional view of the film | membrane structure on a board | substrate. It is a longitudinal cross-sectional view of the film | membrane structure after an etching. And a flow rate ratio of N ₂ gas is a graph showing the relationship between the etching rates of SOG film and the TEOS film. It is a longitudinal cross-sectional view of the film | membrane structure with an unevenness | corrugation in a base film. And a flow rate ratio of N ₂ gas is a graph showing the relationship between the amount of chipping of the resist film and laminated film. Where the N ₂ gas supplied to the O ₂ gas is a diagram showing an actual etching state when supplied. Where the N ₂ gas supplied to the O ₂ gas is a table showing the etch selectivity with respect to the titanium nitride film when supplied. It is a longitudinal cross-sectional view of the film | membrane structure for demonstrating the difference in the arrival time to the base film of an etching.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Etching apparatus 10 Processing container 13 Susceptor 30 Upper electrode 41-44 Gas supply source S Processing chamber W Substrate

Claims (11)

A method of etching a stacked film formed on a substrate and having a plurality of silicon-based insulating films,
The laminated film includes a coated silicon insulating film formed by a coating method,
An etching method comprising introducing an etching gas containing a fluorocarbon gas and a nitrogen gas and not containing an oxygen gas into a processing chamber, and etching the laminated film on the substrate in the processing chamber. The etching method according to claim 1, wherein the coated silicon-based insulating film is an SOG film. 3. The etching according to claim 1, wherein the ratio of the etching rate of the coated silicon-based insulating film and the other silicon-based insulating film is adjusted by adjusting the amount of nitrogen gas introduced. Method. 4. The laminated film includes a CVD silicon-based insulating film formed by a chemical vapor deposition method in addition to the coated silicon-based insulating film. Etching method. The etching method according to claim 4, wherein the CVD silicon-based insulating film is a silicon oxide film. 6. The etching method according to claim 5, wherein the amount of nitrogen gas introduced is adjusted to a flow rate of 30 to 40% of the total flow rate of the etching gas. The etching method according to claim 1, wherein the base film of the laminated film is a nitrogen-based metal film. The etching method according to claim 7, wherein the nitrogen-based metal film is titanium nitride. The program for making a computer implement | achieve the etching method in any one of Claims 1-8. A computer-readable recording medium recording a program for causing a computer to implement the etching method according to claim 1. The plasma processing apparatus which has a control part which performs the etching method in any one of Claims 1-8.

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