JP2005183627A - Unreacted titanium film removal method, semiconductor device manufacturing method, unreacted titanium film removal apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing unreacted titanium film, a method for manufacturing a semiconductor device, and a device for removing unreacted titanium film, which can reduce Ti residue generated on a substrate after removing unreacted titanium film. To do.
A titanium film is formed on a silicon substrate, the titanium film and the silicon are reacted to form a titanium silicide film, and then the unreacted titanium film remaining on the silicon substrate is replaced with the silicon substrate. A method of removing the unreacted titanium film by performing APM on the silicon substrate on which the unreacted titanium film remains to remove the unreacted titanium film from the silicon substrate, and silicon from which the unreacted titanium film has been removed. It includes step A2 for cleaning the substrate with pure water, step A3 for drying the cleaned silicon substrate, and step A4 for applying APM again to the dried silicon substrate.
[Selection] Figure 1

Description

  The present invention relates to a method for removing an unreacted titanium film, a method for manufacturing a semiconductor device, and an apparatus for removing an unreacted titanium film, and in particular, after forming a titanium silicide film on a substrate, the unreacted remaining on the substrate. The present invention relates to a technique for removing a titanium film.

Conventionally, titanium silicide films have been widely used in order to reduce the gate electrode resistance, contact resistance, and the like of transistors (see, for example, Patent Documents 1 and 2).
6A to 6D are process diagrams showing a general method for forming the titanium silicide film 99. In FIG. 6A, 91 is a bulk silicon substrate, 92 is a LOCOS film for element isolation, 93 is a gate oxide film, 94 is a polysilicon gate electrode, 95 is a side wall made of a silicon oxide film, and 96 is an LDD region. 97 are source or drain regions (hereinafter referred to as “S / D regions”). The LDD region 96 is, for example, a low concentration n-type impurity region. The S / D region 97 is, for example, a high concentration n-type impurity region. In FIG. 6A, the titanium silicide film 99 is usually formed on the S / D region 97 and the polysilicon gate electrode 94.

  First, as shown in FIG. 6B, a titanium film 98 is formed on the entire surface of the silicon substrate 91. The titanium film 98 is formed to a thickness of, for example, about 300 [Å] using a sputtering method. Next, the silicon substrate 91 on which the titanium film 98 is formed is subjected to heat treatment, and the portion where the silicon and the titanium film 98 are in contact is silicided. As a result, a titanium silicide film 99 is formed on the S / D region 97 and the polysilicon gate electrode 94 as shown in FIG. The thickness of the titanium silicide film 99 is, for example, about 280 [Å].

  By the way, as shown in FIG. 6C, the silicidation does not proceed at a portion where the insulating film such as the LOCOS film 92 and the sidewall 95 and the titanium film 98 are in contact with each other, and the above-described silicidation does not proceed. Leaves unreacted titanium film (hereinafter referred to as “unreacted titanium film”) 98 ′. Therefore, in the formation process of the titanium silicide film 99, the silicon substrate 91 is usually subjected to wet etching to remove the unreacted titanium film 98 ′ from the LOCOS film 92 and the sidewalls 95.

  FIG. 7 is a flowchart showing a method for removing the unreacted titanium film 98 'according to the conventional example. As shown in FIG. 7, in this method, APM (Ammonium Hydroxide / Hydrogen Peroxide / Water Mixture) is applied to the silicon substrate 91, and the unreacted titanium film 98 ′ left on the silicon substrate 91 is etched and removed. Step S1, Step S2 in which the silicon substrate 91 from which the unreacted titanium film 98 ′ has been removed is cleaned with pure water, and Step S3 in which the cleaned silicon substrate 91 is dried.

In the above step S1, in order to completely remove the unreacted titanium film 98 ′ from the silicon substrate 91, the etching time is excessive with respect to the film thickness of the unreacted titanium film 98 ′ (that is, overetching is performed). ). By performing such steps S1 to S3 on the silicon substrate 91 shown in FIG. 6C, as shown in FIG. 6D, the titanium silicide film 99 remains on the silicon substrate 91 and remains unreacted. Only the titanium film can be removed.
JP 2000-91290 A Japanese Patent Laid-Open No. 9-36360

  By the way, according to the conventional method for removing the unreacted titanium film 98 ′, in order to completely remove the unreacted titanium film 98 ′ from the silicon substrate 91 in step S1 of FIG. 98 'was over-etched with APM. As a result, the unreacted titanium film 98 ′ is completely removed from the silicon substrate 91, and only the titanium silicide film 99 should be left.

  However, actually, despite such over-etching, as shown in FIG. 8, a residue containing titanium (hereinafter referred to as “Ti residue”) 89 occurs on the silicon substrate at a certain frequency. There was a problem. When the Ti residue 89 is generated in this way, the patterns made of the titanium silicide film 99 are short-circuited, which may reduce the yield of the semiconductor device.

  Therefore, the present invention solves such a problem, and it is possible to reduce the Ti residue generated on the substrate after removing the unreacted titanium film, and a method for removing the unreacted titanium film and An object is to provide a method for manufacturing a semiconductor device and an apparatus for removing an unreacted titanium film.

  In order to solve the above-described problem, a first unreacted titanium film removal method according to the present invention includes forming a titanium film on a substrate made of silicon, and reacting the titanium film with the silicon to form titanium silicide. After forming a film, the unreacted titanium film left on the substrate is removed from the substrate, and APM is applied to the substrate on which the unreacted titanium film is left, Removing the unreacted titanium film from the substrate, cleaning the substrate from which the unreacted titanium film has been removed with pure water, drying the cleaned substrate, And again applying APM to the dried substrate.

Further, the second unreacted titanium film removal method according to the present invention is the above-described first semiconductor device manufacturing method, before applying the APM to the substrate on which the unreacted titanium film is left. The method includes a step of applying SPM to the substrate, and a step of cleaning the substrate on which the SPM has been applied with pure water.
Here, APM is an abbreviation for Annium Hydroxide / Hydrogen Peroxide / Water Mixture, and is a mixture of ammonia water (NH ₄ OH), hydrogen peroxide water (H ₂ O ₂ ), and pure water (H ₂ O). It is a liquid. As is well known, this APM has a function of removing particles and organic substances and a function of dissolving titanium. This APM is also called “SC-1”.

SPM is an abbreviation for Sulfuric / Hydrogen Peroxide / Water Mixture, which is a mixture of sulfuric acid (H ₂ SO ₄ ), hydrogen peroxide (H ₂ O ₂ ), and pure water (H ₂ O). That is. As is well known, this SPM has a function of removing metal ions and organic substances and a function of dissolving titanium.
The inventor conducted an experiment to remove the unreacted titanium film using the above APM or the like, and found the following [1] to [3] from the result.

  [1] After removing the unreacted titanium film remaining on the substrate by over-etching using APM (hereinafter referred to as “first APM treatment”), the substrate is washed and dried. Then, APM is again applied to the dried substrate (hereinafter referred to as “second APM treatment”). Then, Ti (titanium) residue generated on the substrate can be reduced as compared with the case where only the first APM treatment is performed as in the prior art.

  [2] In the above [1], when the drying step between the first APM treatment and the second APM treatment is omitted, the removal effect of Ti residue can be obtained to the same extent as in the prior art. Absent. Further, when the above drying step is omitted, the Ti residue can be removed even if the substrate is immersed in the first APM process and the second APM process, or even if the substrate is immersed in the same container. The effect is only as good as the prior art. That is, the effect of removing the Ti residue largely depends on whether or not the above-described drying process is present, not the degree of cleaning of the APM stored in the basket.

  [3] In the above [1], if an unreacted titanium film remains on the substrate when the first APM treatment is completed, an oxide of titanium is formed on the surface of the unreacted titanium film in the next drying step. Will be formed. For this reason, Ti residue cannot be effectively removed by the second APM treatment. That is, in order to enhance the effect of removing Ti residue, it is necessary to remove the unreacted titanium film almost completely by the first APM treatment.

According to the first and second unreacted titanium film removal methods according to the present invention, the unreacted titanium film is almost completely removed by the first APM treatment, and before the second APM treatment is started. The substrate is once dried. Therefore, compared with the prior art, Ti (titanium) residue generated on the substrate after removing the unreacted titanium film can be reduced.
A method for manufacturing a semiconductor device according to the present invention includes the above-described first and second methods for removing an unreacted titanium film. According to the method for manufacturing a semiconductor device according to the present invention, the first and second unreacted titanium film removal methods described above are applied, so that the unreacted titanium film was removed and then generated on the substrate. Ti (titanium) residue can be reduced, which can contribute to an improvement in the yield of the semiconductor device.

  The unreacted titanium film removing apparatus according to the present invention has a titanium film formed on a substrate made of silicon, and the titanium film reacts with the silicon to form a titanium silicide film. An apparatus for etching and removing the unreacted titanium film from the substrate, comprising: an APM tank storing APM; a pure water tank storing pure water; and a dryer for drying the substrate. The substrate on which the unreacted titanium film is left is immersed in the APM soot, the unreacted titanium film is removed from the substrate, and the unreacted titanium film is removed from the substrate. The substrate is washed by immersing in the pure water bath, the washed substrate is placed in the dryer, the substrate is dried, and the dried substrate is immersed again in the APM cage. It is what.

  According to the unreacted titanium film removing apparatus according to the present invention, Ti residue generated on the substrate after removing the unreacted titanium film can be reduced as compared with the prior art.

Hereinafter, an unreacted titanium film removal method, a semiconductor device manufacturing method, and an unreacted titanium film removal apparatus according to an embodiment of the present invention will be described with reference to the drawings.
(1) First Embodiment FIG. 1 is a flowchart showing a method for removing an unreacted titanium film 98 'according to a first embodiment of the present invention. Hereinafter, a method for removing the unreacted titanium film 98 ′ (see FIG. 6C) will be described with reference to this flowchart.

  First, APM (SC-1) is applied as an etchant to the silicon substrate 91 shown in FIG. Thereby, the organic substance is removed from the silicon substrate 91, and the unreacted titanium film 98 'is removed (step A1). In this step A1, in order to completely remove the unreacted titanium film 98 'from the silicon substrate 91, the condition of the wet etching by APM is excessive (that is, exceeded) with respect to the film thickness of the unreacted titanium film 98'. Etching). For example, when the film thickness of the unreacted titanium film 98 ′ is about 300 to 1000 [Å] on average, the etching time by APM in this step A1 is set to about 20 to 45 [min]. This etching by APM is performed, for example, by immersing the silicon substrate 91 in a bag containing APM.

  Next, the silicon substrate 91 to which APM is adhered is cleaned with pure water and cleaned (step A2). This cleaning of the silicon substrate 91 with pure water (hereinafter referred to as “pure water rinse”) is performed, for example, for about 3 to 5 [minutes]. This pure water rinsing is performed, for example, by immersing the silicon substrate 91 in a bowl filled with pure water. Next, the silicon substrate 91 that has been subjected to pure water rinsing is set in, for example, a known spin dryer or the like and dried (step A3). Moreover, IPA vapor drying, Marangoni drying, etc. can also be used as a drying means.

  Next, APM is again applied to the silicon substrate 91 dried in step A3 (step A4). The etching time by APM in this step A4 is, for example, about 5 to 10 [minutes], and may be shorter (that is, light etching) than that in step A1. The light etching in step A4 is performed, for example, by immersing the silicon substrate 91 in a bag containing APM, as in step A1.

  Next, the silicon substrate 91 to which APM is adhered is cleaned with pure water and cleaned (step A5). The pure water rinsing in step A5 is performed, for example, by immersing the silicon substrate 91 in a bowl filled with pure water for about 3 to 5 [minutes], similarly to step A2. Thereafter, the silicon substrate 91 is set on a spin dryer and dried (step A6). Thereby, the removal process of the unreacted titanium film 98 'is completed.

FIG. 3 is a scatter diagram showing the results of an experimental investigation of the relationship between the number of etchings by APM and the number of defects. The horizontal axis in FIG. 3 is a number assigned to distinguish the silicon substrate (wafer), and the vertical axis is the number of defects. The number of defects is the number of Ti residues generated per wafer here.
Further, the rhombus plot of FIG. 3 is the number of defects counted after performing etching and cleaning in steps A1 and A2 of FIG. 1 and drying the wafer in step A3. In addition, the round plot in FIG. 3 selects only wafers that have been counted for many defects after drying in Step 3, performs etching and cleaning in Steps A4 and A5 on the selected wafer, and dries the wafer in Step A6. This is the number of defects counted after.

As can be seen from FIG. 3, when only the first APM process was performed, a wafer with a large number of defects was suddenly generated. On the other hand, when the second APM treatment was performed on a wafer having a large number of defects, the number of defects was greatly reduced, and the yield could be improved by about 20 [%] on average.
In the above investigation, the drying step (step A3) was omitted in FIG. 1, and the second APM treatment (step A4) was continuously performed after the pure water rinse (step A2). However, in this case, the number of defects could not be greatly reduced as in the circular plot of FIG. Also, two jars with APM are prepared instead of one, the drying step (Step A3) is omitted, and the first APM processing (Step A1) and the second APM processing (Step A4) I tried changing the cocoons used in each. However, even in this case, the number of defects could not be greatly reduced as in the circular plot of FIG. Therefore, it was found that the drying process of Step A3 is indispensable, and the defect number cannot be greatly reduced unless this drying process is performed.

  Furthermore, in the above investigation, in FIG. 1, the total processing time by APM was equally divided into two (for example, the first and second APM processes were each set to 20 [minutes]). However, in this case, the unreacted titanium film 98 ′ remains on the silicon substrate 91 by the first APM process (step A1), and titanium is deposited on the surface of the unreacted titanium film 98 ′ by the drying process (step A3). As a result, an oxide is formed. For this reason, the Ti residue could not be removed by the second APM treatment (step A4). Therefore, it was found that the unreacted titanium film 98 'needs to be removed almost completely by the first APM process (step A1).

  FIG. 2 is a conceptual diagram showing an example of the etching apparatus 100 according to the first embodiment of the present invention. The etching apparatus 100 is an example of an apparatus that realizes the wet etching shown in FIG. As shown in FIG. 2, the etching apparatus 100 includes an APM bus 10, a pure water rinse bath 20, a spin dryer 30, a wafer transfer system (not shown), and the like.

  Among these, the APM bus 10 is a bag that stores APM. For example, a circulation pump or a filter is attached to the APM bus 10 so that the APM is circulated while being filtered. The pure water rinsing bath 20 is a tub that stores pure water. For example, pure water is constantly supplied to the pure water rinse bath 20, and the pure water always overflows.

By the way, in this etching apparatus, the wafer transport system sequentially transports a lot made of a plurality of silicon substrates (wafers) in the order of A → B → C → A → B.
That is, first, a lot of a plurality of silicon substrates on which an unreacted titanium film remains is immersed in the APM bus 10. The immersion time is, for example, about 20 to 45 [minutes]. Next, this lot is taken out from the APM bath 10 and immersed in the pure water rinse bath 20. The immersion time is, for example, about 3 to 5 [minutes]. Next, this lot is taken out from the pure water rinse bath 20 and set in the spin dryer 30. Then, the spin dryer 30 is operated to remove moisture from the front and back surfaces of the silicon substrate.

Next, the dried lot is immersed again in the APM bath 10. The immersion time here is, for example, about 5 to 10 [minutes]. Next, this lot is immersed in the pure water rinse bath 20 for about 3 to 5 minutes, for example. Then, this lot is taken out from the pure water rinse bath 20 and set in the spin dryer 30 to dry the silicon substrate.
Thus, according to the removal method of the unreacted titanium film 98 ′ according to the first embodiment of the present invention, the unreacted titanium film 98 ′ is almost completely removed by the first APM treatment, and the second time The silicon substrate 91 is once dried before the APM process is started. Therefore, compared with the prior art, the Ti residue 89 generated on the silicon substrate 91 after removing the unreacted titanium film 98 'can be reduced, which can contribute to the improvement of the yield of the semiconductor device.

  In the first embodiment, the silicon substrate 91 corresponds to the substrate of the present invention, and the titanium film 98 corresponds to the titanium film of the present invention. The titanium silicide film 99 corresponds to the titanium silicide film of the present invention, and the unreacted titanium film 98 'corresponds to the unreacted titanium film of the present invention. Further, the APM bath 10 corresponds to the APM bottle of the present invention, the pure water rinse bath 20 corresponds to the pure water tank of the present invention, and the spin dryer 30 corresponds to the dryer of the present invention. The etching apparatus 100 corresponds to the apparatus for removing an unreacted titanium film of the present invention.

In the first embodiment, the case where APM is used as the chemical solution for dissolving the unreacted titanium film 98 'has been described. However, in FIG. 1, APM may be replaced with SPM. In this case, titanium can be dissolved by SPM, and Ti residue can be reduced.
(2) Second Embodiment FIG. 4 is a flowchart showing a method for removing an unreacted titanium film 98 ′ according to a second embodiment of the present invention. The second embodiment is different from the first embodiment in that preprocessing by SPM is performed before the first APM processing. Other points are the same as in the first embodiment. Therefore, in FIG. 4, the same processing steps as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, in the second embodiment, first, SPM is performed on the silicon substrate 91 shown in FIG. 6C (step B1). Thereby, organic substances and metal ions are removed from the silicon substrate 91. Further, since SPM dissolves titanium, the unreacted titanium film 98 'on the silicon substrate 91 is also etched to some extent. The etching time by SPM in step B1 is, for example, about 10 to 20 [minutes].

  Next, the silicon substrate 91 to which the SPM is adhered is cleaned with pure water and cleaned (step B2). This pure water rinsing is performed, for example, by immersing the silicon substrate in a bowl containing pure water for about 3 to 5 minutes. The subsequent steps are the same as in the first embodiment. That is, after the silicon substrate 91 is rinsed with pure water in step B2 of FIG. 4, the process proceeds to step A1. Then, step A1 to step A6 are sequentially performed.

  FIG. 5 is a conceptual diagram showing an example of an etching apparatus 200 according to the second embodiment of the present invention. The etching apparatus 200 is an example of an apparatus that realizes the wet etching shown in FIG. 5, parts having the same configuration as that of the etching apparatus 100 shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 5, the etching apparatus 200 includes an SPM bus 40, a first pure water rinse bath 50, an APM bus 10, a second pure water rinse bath 20, a spin dryer 30, and a wafer transfer system (not shown). And the like.

  In this etching apparatus 200, the wafer transport system sequentially transports a lot composed of a plurality of silicon substrates (wafers) in the order of a → b → c → d → e → c → d. That is, first, a lot consisting of a plurality of silicon substrates on which an unreacted titanium film remains is immersed in the SPM bus 40. The immersion time is, for example, about 10 to 20 [minutes]. Next, this lot is taken out from the SPM bath 40 and immersed in the first pure water rinse bath 50. The immersion time is, for example, about 3 to 5 [minutes]. Next, this lot is taken out from the first pure water rinse bath 50 and immersed in the APM bath 10. The subsequent lot processing is the same as that of the etching apparatus 100 shown in FIG.

  As described above, according to the method for removing the unreacted titanium film 98 'according to the second embodiment of the present invention, it is possible to obtain the same effects as those of the first embodiment. Further, since the pretreatment by SPM is performed before the etching treatment by APM, metal ions can be particularly effectively removed. This can contribute to the cleaning of the semiconductor device. In the second embodiment, the etching apparatus 200 corresponds to the unreacted titanium film removing apparatus of the present invention.

  In the first and second embodiments described above, the bulk silicon substrate 91 is exemplified as the substrate of the present invention. However, the substrate of the present invention is not limited to this, for example, an SOI (silicon on insulator) substrate. good. When the substrate of the present invention is an SOI substrate, Ti residue 89 can be reduced as in the first and second embodiments, which can contribute to an improvement in the yield of the semiconductor device.

The flowchart which shows the removal method of unreacted titanium film | membrane 98 'which concerns on 1st Embodiment. The conceptual diagram which shows an example of the etching apparatus 100 which concerns on 1st Embodiment. The scatter diagram which shows the result of having investigated experimentally the relationship between the frequency | count of the etching by APM, and the number of defects. 9 is a flowchart showing a method for removing an unreacted titanium film 98 ′ according to the second embodiment. The conceptual diagram which shows an example of the etching apparatus 200 which concerns on 2nd Embodiment. FIG. 6 is a process diagram showing a general method for forming a titanium silicide film 99. The flowchart which shows the removal method of the unreacted titanium film | membrane 98 'which concerns on a prior art example. The figure which shows an example of Ti residue 89. FIG.

Explanation of symbols

  10 APM bus, 20 (second) pure water rinse bath, 30 spin dryer, 40 SPM bath, 50 first pure water rinse bath, 89 Ti residue, 91 silicon substrate, 92 LOCOS film, 93 gate oxide film, 94 polysilicon gate electrode , 95 sidewall, 96 LDD region, 97 S / D region, 98 titanium film, 98 ′ unreacted titanium film, 99 titanium silicide film, 100, 200 etching apparatus

Claims (4)

After forming a titanium film on a substrate made of silicon and reacting the titanium film with the silicon to form a titanium silicide film, the unreacted titanium film left on the substrate is removed from the substrate. A method of removing,
Applying APM to the substrate on which the unreacted titanium film remains, and removing the unreacted titanium film from the substrate;
Washing the substrate from which the unreacted titanium film has been removed with pure water;
Drying the cleaned substrate;
And re-applying APM to the dried substrate. A method for removing an unreacted titanium film.   Before the APM is applied to the substrate on which the unreacted titanium film remains, and a step of applying SPM to the substrate and a step of cleaning the substrate on which the SPM has been applied with pure water. The method for removing an unreacted titanium film according to claim 1, wherein:   A method for manufacturing a semiconductor device, comprising the method for removing an unreacted titanium film according to claim 1. A titanium film is formed on a substrate made of silicon, the unreacted titanium film remaining on the substrate after the titanium film and the silicon react to form a titanium silicide film is etched, An apparatus for removing from a substrate,
An APM tank storing APM, a pure water tank storing pure water, and a dryer for drying the substrate;
The substrate on which the unreacted titanium film is left is immersed in the APM soot, and the unreacted titanium film is removed from the substrate.
The substrate from which the unreacted titanium film has been removed is immersed in the pure water bath to wash the substrate,
Placing the cleaned substrate in the dryer and drying the substrate;
An apparatus for removing an unreacted titanium film, wherein the dried substrate is immersed again in the APM cage.