JP2006210778A - Manufacturing method of semiconductor device, and etchant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To selectively etch TiW films and improve its etching speed. <P>SOLUTION: In manufacturing a semiconductor device 100, an etchant containing hydrogen peroxide and transition metal ions is used to selectively remove a second TiW film 115 and a first TiW film 111. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device and an etching solution.

  In a semiconductor device, a TiW film may be used. The TiW film is used, for example, in a pad region of a semiconductor chip that is flip-chip connected. When the TiW film is used, it may be necessary to remove a predetermined region of the TiW film by wet etching or the like at a predetermined stage in the flip chip manufacturing process. As a technique for wet-etching a TiW film, there is one described in Patent Document 1.

Patent Document 1 describes that hydrogen peroxide (H ₂ O ₂ ) has been used for etching a TiW film. Patent Documents 1 to 3 describe that a liquid obtained by adding a chelating agent to hydrogen peroxide is used as an etchant for a TiW film.

Patent Document 3 describes that the TiW film is etched using a solder layer containing Pb as a mask. At this time, it is said that a chelating agent is used as a material that suppresses redeposition of Pb on the TiW film.
Japanese Patent Laid-Open No. 8-53781 JP 2002-155382 A JP 2000-106362 A

  However, when the present inventors have examined the techniques described in Patent Documents 1 to 3, the etching rate of the TiW film is improved while suppressing etching of other metal films stacked on the TiW film. There was room for improvement.

  For example, according to Patent Document 2, when hydrogen peroxide and a chelating agent are included in the etching solution, the chelating agent forms a complex with Ti ions or W ions in the TiW film. However, as a result of studies by the present inventors, it has been found that addition of a chelating agent facilitates dissolution of not only the TiW film but also other metal films in the etching solution. And the etching rate of the other metal film formed on the upper part of the TiW film is increased, causing side etching.

  In addition, Patent Document 1 and Patent Document 3 also have the same problems because the etching solution contains hydrogen peroxide and a chelating agent.

According to the present invention,
Providing a TiW film on top of the semiconductor substrate;
Selectively removing the TiW film using a chemical solution,
Provided is a method for manufacturing a semiconductor device, wherein the chemical solution contains hydrogen peroxide and transition metal ions.

  According to this manufacturing method, since the TiW film is selectively removed using a chemical solution containing hydrogen peroxide and transition metal ions, the etching rate of the TiW film can be selectively increased. Therefore, the TiW removal process can be shortened by TAT (Turn Around Time). Although this mechanism is not necessarily clear, it is presumed that the radical of hydrogen peroxide in the chemical solution was activated by the transition metal ion and promoted the etching reaction.

  Note that in this specification, the TiW film is a film mainly containing Ti and W and mainly made of Ti and W, but may contain a third component such as N. Moreover, in this specification, a transition metal ion refers to the element contained in 3-11 genus of a long period type periodic table. More specifically, ions of one or more metals selected from the group consisting of Ti, V, Cr, Fe, Co, Ni, Cu, Ru, Rh, Ta and W can be mentioned. Among these, Cu, Ti, or W ions are preferable, and Cu ions are preferably included.

  In the method for manufacturing a semiconductor device of the present invention, the chemical solution can be configured to substantially not contain a chelating agent. By doing so, the TiW film can be further selectively removed.

  In the present specification, “substantially not containing a chelating agent” means that the chelating agent is not intentionally added to the chemical solution, and more specifically, the chelating agent in the chemical solution. The concentration of is, for example, 0.001% by mass or less.

  It should be noted that any combination of these components, or a conversion of the expression of the present invention between a method, an apparatus, and the like is also effective as an aspect of the present invention.

  For example, according to the present invention, there is provided an etching solution for removing a TiW film, which contains hydrogen peroxide, transition metal ions, and does not substantially contain a chelating agent. According to this etching solution, the TiW film can be selectively and rapidly etched.

  According to the present invention, a technique for selectively removing a TiW film quickly is realized by selectively removing the TiW film using a chemical solution containing hydrogen peroxide and transition metal ions.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, common constituent elements are denoted by the same reference numerals, and description thereof is omitted as appropriate.

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the semiconductor device of this embodiment. In the semiconductor device 100 shown in FIG. 1, a multilayer film 102 and an interlayer insulating film 103 are stacked in this order on a silicon substrate 101. A wiring is provided at a predetermined position on the multilayer film 102, and the wiring is embedded in the interlayer insulating film 103. The wiring has a configuration in which a TiN / Ti film 105, an Al wiring 107, and a TiN / Ti film 105 are laminated in this order. A part of the upper surface of the wiring is an opening from which the interlayer insulating film 103 has been removed, and the wiring exposed from the interlayer insulating film 103 is in contact with the first TiW film 111 of the electrode pad. On top of the first TiW film 111, a Cu film 113 and a second TiW film 115 are laminated in this order to constitute an electrode pad. The first TiW film 111, the Cu film 113, and the second TiW film 115 are covered with the polyimide film 109 over the entire side surfaces and part of the upper surface. In the exposed portion from the polyimide film 109, the second TiW film 115 is removed and the upper surface of the Cu film 113 is exposed, and a solder ball 117 is provided on the polyimide film 109 in contact with the Cu film 113. Yes.

Next, a method for manufacturing the semiconductor device 100 will be described. In the present embodiment and the following embodiments, a case where wet etching during a manufacturing process is performed by single wafer processing will be described as an example.
The manufacturing method of this embodiment includes a step of providing a TiW film (second TiW film 115, first TiW film 111) on a semiconductor substrate (silicon substrate 101) and a second using a chemical (etching solution). The step of selectively removing the TiW film 115 or the first TiW film 111, and the chemical solution contains hydrogen peroxide and transition metal ions. In this manufacturing method, the chemical solution can be configured to substantially contain no chelating agent.
After the step of providing the second TiW film 115 and before the step of selectively removing the first TiW film 111 or the second TiW film 115, an insulating protective film is formed on the second TiW film 115. The step of selectively removing the first TiW film 111 or the second TiW film 115 includes the step of providing the (photoresist film 121), and the step of selectively removing the first TiW film 111 or the second TiW film 115 using the photoresist film 121 as a mask. The step of selectively removing a part of the TiW film 115 is included.
Further, after the step of providing the first TiW film 111 and before the step of selectively removing a part of the first TiW film 111, a transition is made as a catalyst supply source on the upper portion of the first TiW film 111. The step of selectively removing the first TiW film 111, including the step of providing a film containing metal (Cu film 113), includes at least part of the Cu film 113 exposed to the chemical solution, and the transition metal A step of selectively removing a part of the first TiW film 111 using ions (Cu ions) as a catalyst is included. The film containing a transition metal is a Cu film.
More specifically, the step of providing the electrode pad includes the step of providing an electrode pad (laminated film of the first TiW film 111, the Cu film 113 and the second TiW film 115) on the silicon substrate 101. After the step of providing one TiW film 111, the step of providing a Cu film 113 as a catalyst supply source on the first TiW film 111, and the step of forming the Cu film 113, the upper portion of the first TiW film 111 is formed. A step of forming a photoresist film 121 in a predetermined region, a step of selectively removing a part of the Cu film 113 using the photoresist film 121 as a mask, and exposing a side surface of the Cu film 113; Removing the TiW film 111 selectively. The step of selectively removing the second TiW film 115 is a step of bringing a dummy substrate provided with the Cu film 113 on the silicon substrate 101 into contact with the chemical solution and supplying Cu ions from the dummy substrate into the chemical solution. After the step of supplying Cu ions, a step of bringing the second TiW film 115 of the semiconductor device 100 into contact with a chemical solution is included.
Further, the step of selectively removing the first TiW film 111 and the second TiW film 115 selectively uses a part of the TiW film 111 with Cu ions as a catalyst while using the photoresist film 121 as a mask. Removing.
In the step of selectively removing the first TiW film 111 and the second TiW film 115, a chemical solution is circulated to perform processing such as single wafer processing.
The step of selectively removing the first TiW film 111 and the second TiW film 115 is performed on the surface of the silicon substrate 101 where the TiW film is formed while the silicon substrate 101 is held horizontally and rotated. It includes a step of supplying a chemical solution through a nozzle and removing the TiW film.
The temperature of the chemical solution is 20 ° C. or higher and 40 ° C. or lower. Further, the concentration of hydrogen peroxide in the chemical solution can be set to 5% by mass or more and 30% by mass or less.
Further, the transition metal ion may be one or more transition metal ions selected from the group consisting of Ti, V, Cr, Fe, Co, Ni, Cu, Ru, Rh, Ta, and W.

  Hereinafter, the manufacturing method of the semiconductor device 100 will be described in more detail with reference to the drawings. 2A to FIG. 2C, FIG. 3A to FIG. 3C, and FIG. 4 are cross-sectional views showing manufacturing steps of the semiconductor device 100 shown in FIG. 2A to FIG. 2C, FIG. 3A to FIG. 3C, and FIG. 4, the silicon substrate 101 and the multilayer film 102 are not shown, and the layers above the interlayer insulating film 103 are not shown. Indicates.

First, as shown in FIG. 2A, a multilayer film 102 (not shown) in which a wiring layer, an interlayer insulating film, and the like are laminated is formed on a silicon substrate 101 (not shown). Then, a wiring layer in which the TiN / Ti film 105, the Al wiring 107, and the TiN / Ti film 105 are laminated in this order is formed on the uppermost interlayer insulating film. Next, an interlayer insulating film 103 having a two-layer structure containing SiON and SiO ₂ is formed, and an opening 119 opening from the wiring layer surface is formed in the interlayer insulating film 103 (FIG. 2A).

  Subsequently, a first TiW (titanium tungsten) film 111, a Cu (copper) film 113 and a second TiW film 115 functioning as an adhesion film are sequentially formed on the interlayer insulating film 103 (FIG. 2B). . The film thicknesses of the first TiW film 111, the Cu film 113, and the second TiW film 115 are, for example, 200 nm, 3000 nm, and 50 nm, respectively. 2B and the like schematically show the configuration of the semiconductor device 100, the thicknesses of the first TiW film 111 and the second TiW film 115 are shown to be approximately the same for convenience. Yes. The Cu film 113 is formed so as to fill the opening 119.

  Thereafter, the first TiW film 111, the Cu film 113, and the second TiW film 115 are patterned to a size suitable for mounting the solder ball 117, thereby forming a pad electrode. Specifically, a photoresist film 121 covering the upper part of the pad electrode formation region is patterned on the second TiW film 115 (FIG. 2C). Then, using the photoresist film 121 as a mask, the second TiW film 115, the Cu film 113, and the first TiW film 111 are sequentially wet etched, and the region immediately below the photoresist film 121 is used as a pad electrode (FIG. 3A). )). In this embodiment, a dummy run using a dummy wafer is performed before wet etching of the second TiW film 115. This point will be described later.

  After the pad electrode is formed, the photoresist film 121 is peeled off (FIG. 3B). Then, a polyimide film 109 is formed by a coating method so as to cover the pad electrode. Subsequently, the polyimide film 109 is patterned to provide an opening 123 to expose a part of the pad electrode (FIG. 3C). Thereafter, using the polyimide film 109 as a mask, the second TiW film 115 at the bottom of the opening 123 is removed by wet etching to obtain the structure shown in FIG. Thereafter, a solder ball 117 in contact with the second TiW film 115 is formed so as to fill the opening 123, whereby the semiconductor device 100 shown in FIG. 1 is obtained.

Among the above manufacturing steps, wet etching of a metal film using the photoresist film 121 as a mask, which is performed after the configuration shown in FIG. 2C is obtained, is performed according to the following procedure in this embodiment.
(Step 1) Dummy wafer etching: Hydrogen peroxide solution of 5% by mass to 30% by mass is used as an etching solution. This etchant does not contain a chelating agent.
(Step 2) Second TiW film 115 etching: Etching solution after dummy wafer etching is used.
(Step 3) Cu film 113 etching: SPM (sulfuric acid-hydrogen peroxide-water) is used.
(Step 4) First TiW film 111 etching: Hydrogen peroxide solution of 5% by mass to 30% by mass is used as an etching solution. This etchant does not contain a chelating agent.
Hereinafter, the etching method of each film will be described in more detail.

The etching in steps 1 to 4 is performed by, for example, single-wafer processing with liquid circulation.
In the single wafer type, processing is performed for each substrate, the substrate is horizontally fixed on a holding table, and the substrate is rotated within the substrate surface while spraying an etching solution on the surface thereof through a nozzle. is there. By adopting the single wafer type, it is possible to more stably control the component concentration in the etching solution and the temperature of the etching solution in the vicinity of the element formation surface of the silicon substrate 101.

  In addition, the processing by liquid circulation is a method of circulating an etching solution after processing the first substrate and using it as a chemical solution for selective etching of the second substrate. By carrying out like this, the process of step 1-step 2 can be implemented still more efficiently. In addition, the transition metal ion concentration in the etching solution at the time of etching the second substrate can be more reliably adjusted.

  Therefore, by using a single-wafer system with liquid circulation, it is possible to control the concentration of transition metal ions in the etching solution and the temperature of the etching solution in the vicinity of the surface of the element formation surface more precisely for each product wafer. Thus, the etching process can be performed more stably.

  The apparatus used for etching in Steps 1 to 4 includes a single-wafer chamber, and rotates a chemical tank that stores an etching solution, a holding unit that holds the silicon substrate 101, and the silicon substrate 101 that is held by the holding unit. Rotating means, etching solution supplying means for supplying an etching solution onto the silicon substrate 101 held by the holding means, and etching solution collecting means for collecting the etching solution supplied on the silicon substrate 101 into a chemical bath. .

  The etching solution is supplied to the silicon substrate 101 so that the etching solution is in contact with the entire element formation surface of the silicon substrate 101, and the etching solution is supplied continuously or intermittently or after the supply. For example, the second TiW film 115 can be removed. At that time, by holding and rotating the silicon substrate 101 on a rotatable stage, the surface of the silicon substrate 101 and the etching solution can be evenly contacted, and more effective cleaning can be performed. Further, when the supply of the etching solution is started, the etching solution is rotated at a relatively high speed so that the etching solution is quickly spread over the entire silicon substrate 101, and thereafter, the etching solution is rotated at a relatively low speed or stopped for a predetermined time. Also good.

  Of Steps 1 to 4, Step 1 and Step 2 are processes for etching the second TiW film 115, and Step 1 is a preliminary process for Step 2. In the present embodiment, the concentration and temperature of the hydrogen peroxide solution are set to predetermined values, and then the dummy wafer is processed in Step 1 and the etching solution after processing the dummy substrate is used under predetermined conditions. By performing the etching of the second TiW film 115 in step 2, the second TiW film 115 can be selectively and rapidly etched for the first time.

The dummy wafer used in Step 1 has a silicon wafer and a film containing a transition metal provided on the silicon wafer.
In this specification, the dummy wafer is a wafer used for etching a TiW film provided on a target product wafer. The dummy wafer only needs to have a structure in which a film containing a transition metal is exposed on the wafer. The dummy wafer may be a wafer in the same state as the product wafer before being subjected to the processing in Step 1 or a wafer having a different structure. Also good. When a wafer having a configuration different from that of the product wafer is used as a dummy wafer, for example, a predetermined film containing a transition metal can be provided on the entire surface of the silicon wafer.

  Examples of the transition metal in the film having a transition metal include Cu, Ti, W, Ni, Ta, and Co. Since these metals are contained in a metal film normally used in a semiconductor device, a dummy wafer can be more easily produced by using a film containing these metals. Further, among these metals, for example, by using Cu, Ti or W, more preferably Cu, the etching rate of the TiW film can be remarkably increased with a small addition amount. Further, the transition metal in the film may be at least one of V, Cr, Fe, Ni, Ru, Rh, and Ta. Since these metals also have a catalytic action of oxidation reaction by hydrogen peroxide like Cu, Ti, and W, the TiW film can be etched more rapidly by using a film containing these metals.

  In Step 1, the concentration of hydrogen peroxide in the etching solution is set to 5% by mass or more and 30% by mass or less, for example. By setting the content to 5% by mass or more, the surface of the TiW film can be more reliably oxidized. By setting the content to 30% by mass or less, the product wafer can be etched more stably. In addition, the stock solution of the commercially available hydrogen peroxide solution is 30% by mass.

  The temperature of the etching solution can be set to 20 ° C. or higher, preferably 25 ° C. or higher, for example. By doing so, the second TiW film 115 can be etched more efficiently. The temperature of the etching solution can be set to 40 ° C. or lower, preferably 35 ° C. or lower, for example. By doing so, the second TiW film 115 can be etched more stably.

  In step 1, hydrogen peroxide solution having a predetermined concentration is placed in a chemical bath and maintained at a predetermined temperature. In addition, a dummy wafer is set in the chamber, and the dummy wafer is rotated around the central axis. Then, an etching solution is sprayed from the nozzle connected to the chemical bath to the formation surface of the film containing the transition metal of the dummy wafer in the chamber. The used etching solution is collected from the chamber and returned to the chemical solution tank. By doing so, transition metal ions can be reliably supplied from the dummy wafer into the etching solution by a simple method.

  In step 2, a liquid containing transition metal ions and hydrogen peroxide and substantially free of a chelating agent is used as an etchant when performing wet etching of the second TiW film 115. This etching solution is obtained by performing wet etching of the dummy wafer on which the film containing the transition metal is formed in hydrogen peroxide water in Step 1. After the dummy wafer is etched, the product wafer is continuously etched using the same etching solution. Specifically, after the dummy wafer in the chamber is taken out, the product wafer is put in and rotated, and the etching solution after processing the dummy wafer is sprayed from the nozzle.

  In Step 2, the temperature of the etching solution can be set to the temperature range exemplified in the processing of the dummy wafer in Step 1, for example, and can be set to a predetermined temperature within this range.

  In the etching of the second TiW film 115 exposed from the polyimide film 109 (FIG. 3C and FIG. 4), the etching is performed in the order of step 1 and step 2. However, the polyimide film 109 is used as a mask instead of the photoresist film 121. Thereby, the etching rate of the second TiW film 115 can be increased and the Cu film 113 can be exposed quickly.

  On the other hand, in step 4, when etching the first TiW film 111, the concentration of hydrogen peroxide, the concentration of transition metal ions, and the etching temperature in the etching solution are set to predetermined values, and the etching method is used. By appropriately selecting, the product wafer can be etched without etching the dummy wafer. Hereinafter, the reason will be described.

  The second TiW film 115 described above forms the uppermost layer of the laminated film, and the upper surface is exposed in the photoresist film 121 or the opening 123. For this reason, a trace amount of transition metal ions can be supplied into the etching solution by using a dummy wafer. On the other hand, the first TiW film 111 is provided with a Cu film 113 and a second TiW film 115 on the upper part, and when the first TiW film 111 is etched, the Cu film 113 and the second TiW film 115 are provided. The side of is exposed.

  For this reason, when etching the first TiW film 111, the concentration of hydrogen peroxide, the concentration of transition metal ions, and the etching temperature in the etching solution are set to predetermined values, and the etching method is appropriately selected. Thus, a trace amount of Cu ions, Ti ions, and W ions can be supplied to the hydrogen peroxide water from the side surface of the film without dissolving the Cu film 113 or the second TiW film 115.

  At this time, since metal ions can be supplied into the etching solution without dissolving the side surfaces of the Cu film 113 and the second TiW film 115, the side etching of the Cu film 113 and the second TiW film 115 proceeds. The etching rate of the first TiW film 111 can be selectively increased while being suitably suppressed. In this specification, supplying a trace amount of transition metal ions into an etching solution without dissolving a film containing a transition metal means that a trace amount of transition metal ions sufficient to serve as a catalyst for etching a TiW film. Is dissolved in the etching solution. More specifically, when the Cu film 113 is formed on the first TiW film 111, the etching rate of the Cu film 113 in the etching solution is 6 nm / min or less as described later in the experimental example. Say something.

The etching of the Cu film 113 in Step 3 may be any liquid that can selectively remove the Cu film 113 with respect to the photoresist film 121, the second TiW film 115, and the first TiW film 111. _{(H 2 SO 4 + H 2} O 2 + H 2 O) , etc., it can be carried out using a known liquid.

  Note that the selection of the etching solution and the selection of the etching conditions for selectively and rapidly etching the TiW film will be described in more detail in an experimental example to be described later in comparison with the conventional manufacturing method.

Next, the effect of this embodiment will be described.
In the present embodiment, an etching solution containing hydrogen peroxide and transition metal ions is used during the wet etching of the first TiW film 111 and the second TiW film 115 in the manufacturing process of the semiconductor device 100. For this reason, compared with the etching using the conventional hydrogen peroxide solution, an etching rate can be improved and a TiW film | membrane can be etched selectively and rapidly. Therefore, the wet etching process can be shortened by TAT (Turn Around Time) and etching can be performed stably. In the etching of the TiW film, as described above, it is important to control the concentration of transition metal ions in the etching solution, so this effect can be exhibited remarkably by adopting a single wafer processing that circulates the etching solution. Is done.

  Further, in the semiconductor device 100, since the etching solution at the time of wet etching of the TiW film does not contain a chelating agent, the dissolution of the metal film on the upper part of the TiW film and accompanying with the configuration described in Patent Documents 1 to 3 above. It has a configuration in which the progress of side etching is suppressed. This point will be described in more detail in the third embodiment as compared with the conventional method.

  In the semiconductor device 100, a dummy run using a dummy wafer is performed in advance when the second TiW film 115 is etched (FIGS. 2C to 3A and 3C to 4). (Step 1). By performing the dummy run, it is possible to stably adjust the concentration of transition metal ions in the etching solution to a predetermined value by a simple method before processing the product wafer. For this reason, the TiW film on the product wafer can be selectively and rapidly etched and more stably performed.

  In Patent Document 2, it is preferable to set the etching temperature to 70 ° C. However, when an etching solution containing hydrogen peroxide is handled at a relatively high temperature, the convenience of handling the etching solution is also improved. There was room for. On the other hand, in this embodiment, since the TiW film is etched using an etching solution containing transition metal ions, the etching temperature can be set to a relatively low temperature of, for example, 20 ° C. or more and 40 ° C. or less. Therefore, even when the concentration of the hydrogen peroxide solution is high, the convenience of handling the etching solution can be improved and the etching can be performed stably, and the semiconductor device 100 has a configuration with excellent manufacturing stability. It has become.

  In the following embodiment, it demonstrates centering on a different point from 1st embodiment.

(Second embodiment)
In the first embodiment, the wet etching process of the second TiW film 115 in the manufacturing process of the semiconductor device 100 uses the dummy wafer etching process (step 1) and the etching solution after etching the dummy wafer. Product wafer etching process (step 2). In the present embodiment, a method for etching the second TiW film 115 of the product wafer without etching the dummy wafer will be described. After the configuration shown in FIG. 2C is obtained in the second TiW film 115, the second TiW film 115 is wet-etched using the photoresist film 121 as a mask (FIG. 2C, FIG. 3 (a)) and the etching process of the second TiW film 115 using the polyimide film 109 as a mask (FIGS. 3C and 4), the following method can be applied.

  In this embodiment, a liquid containing hydrogen peroxide and transition metal ions and substantially free of a chelating agent such as EDTA is used for etching the second TiW film 115. The concentration of hydrogen peroxide in the etching solution is, for example, a concentration included in the range described above in the first embodiment.

Examples of the transition metal ions in the etching solution include metal ions having a catalytic action for oxidation of the TiW film by hydrogen peroxide. In addition, it is preferable to use metal ions that can be dissolved in hydrogen peroxide to a concentration that can exhibit a catalytic action. Examples of such metals include fourth-period metals such as Ti, V, Cr, Fe, Co, Ni, and Cu;
Examples include metals of the fifth period such as Ru and Rh; metals of the sixth period such as Ta and W, and the like. Among these metals, more specifically, Cu or Ti, more preferably Cu, can be used to significantly increase the etching rate of the TiW film with a small addition amount.

  The concentration of the transition metal ion in the etching solution is not limited as long as the catalytic action can be exerted, and can be experimentally determined according to the type of metal. For example, when an etching solution containing Ti ions is used, the Ti concentration in the etching solution can be, for example, 30 ppb (ng / g) or more, preferably 100 ppb or more. When an etching solution containing Cu ions is used, the Cu concentration in the etching solution can be set to, for example, 5 ppb or more, preferably 10 ppb or more. Further, when an etching solution containing W ions is used, the W concentration in the etching solution can be set to, for example, 1500 ppb or more, preferably 4000 ppb or more. By doing so, the etching rate of the TiW film can be increased more reliably. The upper limit of transition metal ions in the etching solution is not particularly limited as long as selective etching of the TiW film occurs stably. Moreover, the transition metal ion in the etching solution may be one kind or plural kinds.

  According to the present embodiment, since the dummy wafer etching step is not required, in addition to the effect of the first embodiment, the TAT can be further shortened.

(Third embodiment)
In the first and second embodiments, the configuration in which the solder ball 117 (FIG. 1) is connected to the electrode pad has been described as an example. However, the solder ball may be lead-free solder. In the present embodiment, a semiconductor device including solder balls made of lead-free solder will be described.

  FIG. 5 is a cross-sectional view showing the configuration of the semiconductor device of this embodiment. The basic configuration of the semiconductor device 110 illustrated in FIG. 5 is the same as the configuration of the semiconductor device 100 described in the first embodiment, except for the following points. First, the configuration of the pad electrode is different. In the semiconductor device 110, a pad electrode made of a film in which a Ti / TiW film 131, a Cu seed layer 133, a Ni film 135, and a Cu film 137 are stacked in this order from the bottom is provided. Further, the Ti / TiW film 131 and the Cu seed layer 133 are provided from the side surface of the opening of the polyimide film 109 to the upper surface of the polyimide film 109. The material of the solder ball provided in contact with the Cu film 137 is lead-free solder 139.

  Next, a method for manufacturing the semiconductor device 110 shown in FIG. 5 will be described. 6A to FIG. 6C, FIG. 7A to FIG. 7C, FIG. 8A and FIG. 8B are cross-sectional views showing the manufacturing process of the semiconductor device 110. FIG. 6A to FIG. 6C, FIG. 7A to FIG. 7C, FIG. 8A and FIG. 8B, the silicon substrate 101 and the multilayer film 102 are not shown. The layers over the interlayer insulating film 103 are shown.

  First, a multilayer film 102, an interlayer insulating film 103, and a wiring layer (a laminated film of a TiN / Ti film 105, an Al wiring 107, and a TiN / Ti film 105) are sequentially formed on the silicon substrate 101. These members are formed using, for example, the method described in the first embodiment. Next, a polyimide film 109 is formed on the entire surface of the interlayer insulating film 103 by a coating method. Then, an opening 141 that opens from the surface of the polyimide film 109 to the inside of the interlayer insulating film 103 is formed, and a part of the surface of the TiN / Ti film 105 above the wiring is exposed (FIG. 6A).

  Then, a Ti / TiW film 131 functioning as an adhesion film is formed on the polyimide film 109 by a sputtering method (FIG. 6B). The Ti / TiW film 131 has a structure in which, for example, a 200 nm TiW film and a 30 nm Ti film are stacked in this order from the bottom. Next, a Cu seed layer 133 is formed, for example, 300 nm on the Ti / TiW film 131 (FIG. 6C). Subsequently, a resist pattern in which the region above the opening 141 is opened is formed on the Cu seed layer 133, and the Ni film 135 and the Cu film 137 are formed in this order so as to embed the opening 141 on the resist pattern. Form a film. The Ni film 135 and the Cu film 137 are formed by, for example, plating, and the thicknesses of the Ni film 135 and the Cu film 137 are, for example, 3.0 μm and 0.4 μm, respectively. Then, by removing the resist pattern, an electrode pad can be obtained by a lift-off method (FIG. 7A).

  Subsequently, a photoresist film 143 is provided on the entire upper surface of the silicon substrate 101 (not shown). Thereafter, the photoresist film 143 is processed so as to have a shape covering the upper and side surfaces of the pad electrode (FIG. 7B). Subsequently, using the photoresist film 143 as a mask, the Cu seed layer 133 and the Ti / TiW film 131 are sequentially wet etched (FIGS. 7C and 8A). For wet etching of the Cu seed layer 133, for example, the SPM described in the first embodiment is used. The wet etching of the Ti / TiW film 131 will be described in detail below. Then, after removing the photoresist film 143 (FIG. 8B). By forming lead-free solder 139 on the Cu film 137, the semiconductor device 110 shown in FIG. 5 is obtained.

Here, the step of removing the Ti / TiW film 131 in the region exposed from the photoresist film 143 (FIG. 8A),
(Step 5) Wet etching of Ti film: DHF (HF-H ₂ O) is used as an etching solution.
(Step 6) Wet etching of TiW film: 5% by mass or more and 30% by mass or less of hydrogen peroxide water is used as an etching solution. This etchant does not contain a chelating agent.
In order.

  In the semiconductor device 110, a Cu seed layer 133 that functions as a supply source of transition metal ions serving as a catalyst for TiW etching is formed on the Ti / TiW film 131. For this reason, the semiconductor device of the first embodiment is set by setting the concentration of hydrogen peroxide, the concentration of transition metal ions, and the etching temperature in the etching solution to predetermined values, and appropriately selecting the etching method. In the same manner as the first TiW film 111 removal step (step 4) in 100, a very small amount of Cu is supplied from the Cu seed layer 133 into the etching solution while the side etching of the Cu seed layer 133 does not proceed. The TiW film under the / TiW film 131 can be selectively removed by etching. For this reason, also in this embodiment, the etching rate of the TiW film can be increased as in the first embodiment. In addition, the TiW film can be etched with high selectivity with respect to the upper two layers (the Cu seed layer 133 and the Ti film on the Ti / TiW film 131).

  In the semiconductor device 110 according to the present embodiment, the solder ball is composed of lead-free solder 139. In order to obtain an electrode pad corresponding to lead-free solder, the electrode pad is preferably made of a material that prevents diffusion of tin or the like in the solder. Examples of such a material include nickel and a nickel alloy. However, these materials are easily oxidized and have poor solderability. Therefore, in the present embodiment, an electrode pad having a two-layer structure is formed of a Ni film 135 that functions as a barrier metal layer and a Cu film 137 that is formed on the Ni film 135 and functions as a contact layer. For this reason, the lead-free solder 139 can be more stably formed on the electrode pad.

  As the barrier metal layer, the Ni film 135 or nickel alloy used in this embodiment is preferably used. This is because nickel is excellent in barrier performance against diffusion of tin contained in lead-free solder. When a nickel alloy is used in place of the Ni film 135, specifically, a nickel-vanadium alloy can be used. In addition, tungsten, tantalum, silicon, copper, or the like can be selected as an additive component.

  Further, the Cu film 137 functions as a contact layer in direct contact with the lead-free solder 139. As the contact layer, a material having good solderability and low resistance is preferably used. In this embodiment, copper is used. However, as a film containing other transition metal ions, the Cu seed layer 133 may be a film containing transition metal ions of the same type as the contact layer (Cu film 137 in this embodiment). For example, instead of the Cu film 137, a copper-aluminum alloy or the like can be used. It is sufficient for the contact layer to cover the barrier metal layer, and the thickness is preferably 0.5 μm or less. If it is too thick, the ability to prevent diffusion of tin or the like in the lead-free solder 139 may be reduced. When the contact layer is made of copper or a copper alloy, a plating method can be used instead of the sputtering method as a film forming method. By using the plating method, moderate unevenness can be formed on the surface of the Cu film 137 with good controllability, so that the adhesion of the lead-free solder 139 can be further improved.

  In Patent Document 3 described above in the section of the background art, a layer composed of TiWNx, a layer composed of TiW, a layer composed of Cu, and Su and Pb are formed on a bonding pad provided on a substrate. An electronic component in which layers composed of solder are provided in this order from the bottom is described. When manufacturing this electronic component, a solder layer is formed on the Cu layer in advance, and the TiW film is etched using the solder layer as a mask. As the etching solution, it is necessary to use a chemical solution that does not dissolve the mask solder. Specifically, in Patent Document 2, etching is performed using an etching solution containing hydrogen peroxide and a chelating agent.

  In contrast, in the present embodiment, the TiW film in the Ti / TiW film 131 is etched using a resist film, which is an insulating protective film, as a mask. For this reason, the etching solution can be selected without considering the solubility of the lead-free solder 139. In this embodiment, the TiW film is etched using an etchant containing hydrogen peroxide and transition metal ions. Since this etching solution dissolves the solder, it cannot be applied to a manufacturing method using a solder layer as a mask, as in the case of Patent Document 2.

  In addition, the etching solution used in Patent Document 2 includes a chelating agent so that Pb in the solder does not accumulate on the metal film to be etched to prevent the etching. However, as explained in the section of the problem to be solved by the invention, when an etching solution containing a chelating agent is used, the etching rate of other metal layers stacked on the top of the TiW film also increases. Was the cause. Patent Document 2 also describes that when the etching rate of Cu increases, a large undercut occurs in other layers, which may cause reliability and other problems. On the other hand, in the etching of the TiW film, when a chelating agent is present, transition metal ions that are considered to act as a catalyst for the reaction of hydrogen peroxide are trapped by forming a complex with the chelating agent. For this reason, transition metal ions eluted from other metal layers could not function sufficiently as a catalyst for etching the TiW film. For this reason, there is room for improvement in that the etching rate of the TiW film is selectively increased.

  On the other hand, in this embodiment, since the chelating agent itself that increases the etching rate of Cu is not substantially contained, the etching selectivity of the TiW film is improved, and the side of other metal films such as the Cu seed layer 133 is increased. Etching progress is effectively suppressed. For this reason, in the above step 6, it is possible to supply a trace amount of Cu ions from the Cu seed layer 133 into the etching solution while selectively etching the TiW film while suppressing the etching rate of the Cu seed layer 133. The TiW film can be selectively and rapidly wet etched.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  For example, in the above embodiment, a photoresist film is used as a mask when etching a TiW film. However, the insulating film is not limited to a photoresist film, and a film used as a hard mask, for example. Can also be used.

  In the above embodiment, the case where the wet etching of the TiW film is performed by a single wafer type has been described as an example, but dipping type wet etching may be used. For example, the steps 1 and 2 described above in the first embodiment can be performed by the dip method according to the following method. First, a dummy wafer is immersed in a chemical bath containing hydrogen peroxide solution of a predetermined concentration, and a dummy run in step 1 is performed. After the dummy wafer is taken out, the product wafer is immersed in the same chemical bath, and the TiW film 115 in step 2 is etched. By using the dip method, a plurality of wafers can be immersed and processed at one time, so that the etching processing time can be further shortened. In addition, the amount of etching solution used can be reduced.

Hereinafter, the influence of the etching rate of the TiW film formed on the silicon substrate on the composition of the etchant was examined.
(Experimental example 1)
After performing a dummy run for a predetermined time using a dummy wafer having a TiW film formed on a silicon wafer, another wafer having a TiW film formed on another wafer was etched. Then, the relation between the Ti concentration and W concentration in the etching solution after the dummy run and the etching rate of the TiW film was examined. Etching was a liquid circulation type single wafer process. The etching solution at the start of the dummy run was 30% by mass of hydrogen peroxide, and the etching solution after the dummy run was used as it was for etching another wafer. The etching temperature was 20 ° C. The results are shown in FIG. 9 and FIG.

  As shown in FIGS. 9 and 10, it can be seen that the etching rate of the TiW film is increased by the elution of a small amount of Ti and W in the etching solution by the dummy run. When the transition metal ion was not included in the etching solution, the progress of the etching of the TiW film was slow, and it took about 3000 s to etch the 200 nm TiW film. In addition, when the metal ions were dissolved by the dummy treatment, the etching rate was increased and the reproducibility was high.

(Experimental example 2)
In Experimental Example 1, examination was performed in the same manner as in Experimental Example 1 except that the film formed on the dummy wafer was replaced by a Cu film instead of the TiW film. FIG. 11 shows the relationship between the Cu ion concentration in the etching solution and the etching rate of the TiW film. From FIG. 11, it was possible to further improve the etching rate of the TiW film at a transition metal ion concentration lower than that of Experimental Example 1 by using the dummy wafer on which the Cu film was formed.

  In order to investigate the etching characteristics of the Cu film with respect to 30% by mass hydrogen peroxide, the etching time of the dummy wafer and the etching amount of the Cu film were examined. The results are shown in FIG. As shown in FIG. 12, it was found that the etching of the Cu film did not proceed more than about 4 nm even when the processing time was increased. For example, when a dummy wafer having a Cu film was etched for 200 seconds, the Cu film was etched by about 4 nm. This is presumably because the unstable layer on the surface of the Cu film is oxidized by hydrogen peroxide to produce a stable Cu oxide, and this oxide acts as an anticorrosion film.

  From these results, it is considered that even when a Cu film is provided on the TiW film, the etching rate of the TiW film can be remarkably improved by a simple process while suppressing side etching of the Cu film.

(Experimental example 3)
In this experimental example, the silicon wafer provided with the TiW film was etched using an etching solution containing 30 mass% hydrogen peroxide and a chelating agent. As the chelating agent, ethylene dinitrilotetraacetic acid (EDTA) was used, the concentration of EDTA in the etching solution was 0.15 wt%, and the pH of the etching solution was 4.

  When etching was performed at 20 ° C. and 40 ° C., respectively, the etching rate of the TiW film was lower than in Experimental Examples 1 and 2 under any temperature condition.

  Further, when the same examination was performed at 40 ° C. on the silicon wafer in which the TiW film and the Cu film were laminated in this order, the etching selectivity of the TiW film was lowered, and the side etching of the Cu film of 10 μm or more occurred. . In this experimental example, a chelating agent is contained in the etching agent in addition to hydrogen peroxide, so that the oxide generated on the surface of the Cu film is removed by the chelating agent. For this reason, unlike the case of Experimental Example 2, it is assumed that the chain reaction proceeds and the etching proceeds. Moreover, when the same experiment was repeated, the reproducibility of the etching rate of the TiW film was lower than that of Experimental Example 2.

It is sectional drawing which shows the structure of the semiconductor device in embodiment of this invention. FIG. 3 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 1. FIG. 3 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 1. FIG. 3 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 1. It is sectional drawing which shows the structure of the semiconductor device in embodiment of this invention. FIG. 6 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 5. FIG. 6 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 5. FIG. 6 is a process cross-sectional view illustrating a manufacturing procedure of the semiconductor device of FIG. 5. It is a figure which shows the relationship between Ti density | concentration in the etching liquid in an experiment example, and the etching rate of a TiW film | membrane. It is a figure which shows the relationship between W density | concentration in the etching liquid in an experiment example, and the etching rate of a TiW film | membrane. It is a figure which shows the relationship between Cu density | concentration in the etching liquid in an experiment example, and the etching rate of a TiW film | membrane. It is a figure which shows the relationship between the etching time and etching amount of Cu film | membrane in an experiment example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Semiconductor device 101 Silicon substrate 102 Multilayer film 103 Interlayer insulation film 105 TiN / Ti film 107 Al wiring 109 Polyimide film 110 Semiconductor device 111 First TiW film 113 Cu film 115 Second TiW film 117 Solder ball 119 Opening 121 Photo Resist film 123 Opening 131 Ti / TiW film 133 Cu seed layer 135 Ni film 137 Cu film 139 Lead-free solder 141 Opening 143 Photoresist film

Claims (13)

Providing a TiW film on top of the semiconductor substrate;
Selectively removing the TiW film using a chemical solution,
The method for manufacturing a semiconductor device, wherein the chemical solution contains hydrogen peroxide and transition metal ions. In the manufacturing method of the semiconductor device according to claim 1,
The method for manufacturing a semiconductor device, wherein the chemical solution does not substantially contain a chelating agent. In the manufacturing method of the semiconductor device according to claim 1 or 2,
After the step of providing the TiW film, before the step of selectively removing the TiW film, including a step of providing an insulating protective film on the TiW film,
The method of selectively removing a TiW film includes a process of selectively removing a part of the TiW film using the protective film as a mask. In the manufacturing method of the semiconductor device according to claim 1,
After the step of providing the TiW film, before the step of selectively removing a part of the TiW film, including a step of providing a film containing a transition metal as a catalyst supply source on the TiW film,
In the step of selectively removing the TiW film, a part of the TiW film is selectively used with a transition metal ion as a catalyst in a state where at least a part of the film containing the transition metal is exposed in the chemical solution. A method for manufacturing a semiconductor device comprising the step of removing the semiconductor device. In the manufacturing method of the semiconductor device according to claim 1,
Providing an electrode pad on the semiconductor substrate;
The step of providing an electrode pad comprises:
Providing the TiW film;
Providing a transition metal-containing film as a catalyst supply source on the TiW film;
After the step of forming the film containing a transition metal, a step of forming an insulating protective film in a predetermined region on the TiW film;
Using the protective film as a mask, selectively removing a part of the film containing a transition metal and exposing a side surface of the film containing a transition metal;
The step of selectively removing the TiW film;
Including
The step of selectively removing the TiW film includes a step of selectively removing a part of the TiW film using the transition metal ions as a catalyst while using the protective film as a mask. Device manufacturing method. In the manufacturing method of the semiconductor device according to claim 4 or 5,
A method of manufacturing a semiconductor device, wherein the film containing a transition metal is a Cu film. In the manufacturing method of the semiconductor device according to claim 1,
The step of selectively removing the TiW film includes:
Contacting the chemical substrate with a dummy substrate provided with a film containing the transition metal ions on the substrate, and supplying the transition metal ions from the dummy substrate into the chemical solution;
After the step of supplying transition metal ions, the step of bringing the TiW film of the semiconductor device into contact with the chemical solution;
A method for manufacturing a semiconductor device, comprising:   8. The method of manufacturing a semiconductor device according to claim 1, wherein the chemical solution is circulated in the step of selectively removing the TiW film.   9. The method of manufacturing a semiconductor device according to claim 1, wherein the step of selectively removing the TiW film includes the TiW of the semiconductor substrate while the semiconductor substrate is held horizontally and rotated. A method of manufacturing a semiconductor device, comprising: supplying the chemical solution to a film formation surface through a nozzle to remove the TiW film.   10. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the chemical solution is 20 ° C. or higher and 40 ° C. or lower. 11.   11. The method for manufacturing a semiconductor device according to claim 1, wherein the concentration of the hydrogen peroxide in the chemical solution is 5% by mass or more and 30% by mass or less.   12. The method of manufacturing a semiconductor device according to claim 1, wherein the transition metal ion is an ion of one or more transition metals selected from the group consisting of Ti, Cu, and W. A method for manufacturing a semiconductor device. An etching solution for removing a TiW film, which contains hydrogen peroxide and transition metal ions, and does not substantially contain a chelating agent.

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