JP2006073806A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device capable of reducing occurrence of flaws on the surface of a semiconductor substrate in its polishing process. <P>SOLUTION: The surface of the semiconductor substrate is polished by pressing the surface of the semiconductor substrate on a polishing pad at a prescribed pressure, and moving the surface of the semiconductor substrate at a prescribed relative speed with respect to the polishing pad. Then the semiconductor substrate is left from the polishing pad after a buffering step. The relative speed is reduced more than the speed at polishing while the pressing pressure of the surface of the semiconductor substrate onto the polishing pad is kept within a range between the pressing pressure at polishing or below and a pressure of 60% thereof or over. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a CMP (Chemical Mechanical Polishing) technique for polishing a surface of an insulating film or the like deposited on a semiconductor substrate.

  In manufacturing a semiconductor device, the surface of an insulating film deposited on a semiconductor substrate on which a step due to wiring or the like is formed is planarized, or an insulating film is deposited on a semiconductor substrate on which a groove is formed, A CMP method for polishing the surface of an insulating film is widely used for the purpose of removing the portion and leaving a portion embedded in the trench (STI (shallow trench isolation process)). The CMP method also forms a groove or a hole in an insulating film on a semiconductor substrate, removes a portion of the metal material such as tungsten or copper deposited thereon, and removes a portion outside the groove or the hole, and a metal material in the groove or hole. It is also used for the purpose of embedding (damascene or plug forming process).

  In CMP, a semiconductor substrate on which a material to be polished is formed is pressed against a surface plate having a polishing pad on the surface with a constant pressure and moved at a constant relative speed with respect to the polishing pad. The material to be polished on the surface of the substrate is polished by the action of the abrasive grains fixed on the surface or contained in the slurry (polishing liquid) and supplied onto the polishing pad.

  However, scratches (scratches, etc.) occur on the surface of the material to be polished (in the case of planarizing the insulating film) or the underlying material (in the case of STI, plug, damascene) that is exposed after the material to be polished is removed by polishing. It is known that there may be. In particular, when the pressing pressure and the relative speed are increased in order to increase the polishing rate and improve the processing capability, the occurrence of scratches becomes significant.

  In order to prevent or reduce the occurrence of such scratches, it has been proposed to reduce the rotation speed of the surface plate and control the pressure to be low at the end of machining (Patent Document 1).

  Further, in order to reduce the surface roughness after polishing, the semiconductor substrate is transferred to an auxiliary pad different from the polishing pad for polishing, slurry is supplied onto the polishing pad, and slurry buffing (touch-up process) Has been proposed (Patent Document 2).

  Furthermore, in order to prevent the abrasive grains contained in the slurry from aggregating due to a change in pH value (pH shock) due to mixing with pure water and causing scratches, it is proposed to provide means for adjusting the pH value of the slurry. (Patent Document 3).

JP 62-162464 A JP-A-10-202507 JP 2000-326211 A

  However, the pad surface used for polishing contains large-diameter abrasive grains in which the abrasive grains supplied in the slurry are aggregated, debris of the material to be polished, etc., and the substrate to be processed is on the surface. As long as it is pressed and polished, even if the speed and pressure at the end are lowered as proposed in Patent Document 1, the occurrence of scratches is inevitable.

  Further, in Patent Document 2, it is proposed to perform a touch-up process by transferring a semiconductor substrate to an auxiliary pad different from the polishing pad. Specifically, what sequence and conditions should be used. There is no description.

  Further, as a result of studies by the present inventors, it has been clarified that scratches may occur at the timing when the semiconductor wafer is detached from the polishing pad. That is, since the adhesion between the semiconductor wafer and the polishing pad is high, when the semiconductor wafer is detached from the polishing pad, the polishing pad bends and the polishing pad comes into contact with the semiconductor wafer surface, so that the semiconductor wafer surface is scratched. There is a case. Such a method for suppressing the occurrence of scratches at the time of detachment is not shown in the above-described prior art.

  An object of the present invention is to provide a method for manufacturing a semiconductor device that can eliminate the problems based on the conventional technology and reduce the occurrence of scratches on the surface of a semiconductor substrate during polishing.

In order to achieve the above object, the present invention provides a method for pressing a semiconductor substrate surface against a polishing pad with a predetermined pressure and moving the semiconductor substrate surface with respect to the polishing pad at a predetermined relative speed. In removing the semiconductor substrate from the polishing pad after polishing the substrate surface,
Removing the semiconductor substrate after performing a buffering step in which the pressing pressure against the polishing pad is kept within the range of 60% or more during the polishing and the relative speed is decreased as compared with the polishing. A feature of the present invention is to provide a method for manufacturing a semiconductor device.

  Here, it is preferable that the relative speed in the buffering step is reduced to 2/3 to 1/3 of the relative speed during the polishing.

Further, the present invention attaches a semiconductor substrate to a surface plate having a polishing pad, polishes the surface of the semiconductor substrate, and then attaches it to a surface plate having a buff polishing pad provided separately from the polishing pad. In performing buffing,
The semiconductor substrate is mounted while supplying pure water to the surface plate having the buffing pad, and then slurry buffing is performed by supplying slurry containing abrasive grains, and then buffing is performed by supplying pure water. A method for manufacturing a semiconductor device is provided.

Here, polishing performed by attaching to the polishing pad is performed by supplying slurry containing abrasive grains to the polishing pad,
The slurry buffing is preferably performed by supplying the same slurry as that supplied to the polishing pad at a supply amount in a range of ± 25% of the supply amount to the polishing pad.

  Preferably, the polishing pad has a size larger than that of the semiconductor substrate, and the surface of the semiconductor substrate is polished by rotating each of the polishing pad and the semiconductor substrate about different axes. .

  The polishing of the surface of the semiconductor substrate is preferably polishing of a surface layer of an insulating film formed on the entire surface of the semiconductor substrate.

  According to the present invention, it is possible to greatly reduce the occurrence of scratches on the surface of the semiconductor substrate by detaching the semiconductor substrate from the polishing pad after performing the buffering step. Further, according to the present invention, while supplying pure water to the surface plate, by attaching the semiconductor substrate to the surface plate having a buffing pad, the agglomerated abrasive grains adhering to the surface of the semiconductor substrate during the main polishing or Debris of the material to be polished or particles adhering to the buffing pad can be removed. Subsequently, by supplying slurry containing an abrasive flow and performing slurry buff polishing, scratches generated on the surface of the semiconductor substrate during main polishing can be removed, and the yield of manufactured semiconductor devices can be improved.

  Hereinafter, a method for manufacturing a semiconductor device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a schematic view showing a step of polishing the surface of a semiconductor wafer by applying the method for manufacturing a semiconductor device of the present invention. As shown in the figure, a CMP apparatus 11 for applying the semiconductor device manufacturing method of the present invention includes a wafer loader unit 12, a polishing head 24, a main polishing unit 14, a buff polishing unit 16, and a wafer unloader. A portion 18 is provided. The main polishing polishing unit 14 includes a polishing surface plate 22 having a main polishing pad 20 mounted on the upper surface thereof, a pure water supply pipe 26 and a slurry supply pipe 28. The buffing polishing unit 16 includes a polishing surface plate 32 on which a buffing polishing pad 30 is mounted, a pure water supply pipe 36 and a slurry supply pipe 38.

  When polishing the surface of the semiconductor wafer 10 (the surface of the semiconductor substrate that is the surface to be polished), the semiconductor wafer 10 is carried into the CMP apparatus 11 via the wafer loader unit 12, and below the polishing head (semiconductor wafer suction mechanism) 24. Then, the surface to be polished is attracted downward (in the main polishing polishing unit 14 and the buffing polishing unit 16, the surfaces to be polished are directed to the polishing surface plates 22 and 32). Then, it is attached to the main polishing unit 14 while being adsorbed by the polishing head 24, and main polishing is performed there.

  In the polishing unit 14 for main polishing, the polishing surface plate of the semiconductor wafer 10 is pressed while the surface to be polished is pressed against the polishing pad 20 with a predetermined pressure, and slurry containing abrasive grains is supplied from the slurry supply pipe 28 at a predetermined flow rate. 22 and the polishing head 24 are each rotated at a predetermined speed for a predetermined time. That is, the surface of the semiconductor substrate is moved with respect to the polishing pad 20 at a predetermined relative speed. Thereby, the surface of the semiconductor substrate is polished.

  Thereafter, when the semiconductor substrate (that is, the semiconductor wafer 10) is detached from the polishing pad 20, the pressing pressure against the polishing pad 20 is kept within the range of 60% or more during polishing and the relative speed is set to the speed during polishing. A buffering step for polishing the surface of the semiconductor substrate is performed by rotating the polishing surface plate 22 and the polishing head 24 at a predetermined speed for a predetermined time while supplying the slurry from the slurry supply pipe 28 at a predetermined flow rate. After that, the semiconductor substrate is detached from the polishing pad 20.

  The main polishing processing time may be set as appropriate according to the material of the surface to be polished and the required polishing amount. Further, it is preferable that the processing time of the buffering step is extremely short compared with the processing time of the main polishing. Since the purpose of the buffering step is to reduce the deflection of the polishing pad when the semiconductor wafer is subsequently detached from the polishing pad, the rotation of the polishing surface plate 22 and the polishing head 24 is reduced as compared with the polishing. It suffices to go for a period of time to stabilize at the set speed. The specific required speed varies depending on the response speeds of the polishing surface plate 22 and the polishing head 24, but is usually preferably about 5 to 10 seconds.

  As described above, after the main polishing, when the semiconductor wafer 10 is detached from the polishing pad 20, a buffering step is performed, and then the semiconductor substrate is detached from the polishing pad 20. The occurrence of scratches can be reduced.

  In order to obtain a sufficient scratch reduction effect by the buffering step, the polishing surface plate is set so that the relative speed between the polishing pad 20 and the semiconductor wafer 10 is about 2/3 or less of the relative speed during polishing. It is preferable to reduce the rotational speed of the polishing head 22 and the polishing head 24. On the other hand, if the relative speed is decreased too much, the supply of slurry becomes non-uniform and the scratches may increase. Therefore, it is usually preferable to reduce the relative speed during polishing to a range of 2/3 to 1/3, for example, about 1/2.

  The semiconductor wafer 10 after the main polishing is finished is transferred to the polishing unit 16 for buff polishing while being adsorbed by the polishing head 24, where buff polishing is performed.

  In the polishing unit 16 for buff polishing, the semiconductor wafer 10 adsorbed by the polishing head 24 is mounted on the polishing surface plate 32 having the buff polishing pad 30 while supplying pure water from the pure water supply pipe 36. At this time, the semiconductor wafer 10 is not pressed against the buffing pad 30, but is floated on the surface of the buffing pad 30 through pure water.

  By attaching the semiconductor wafer 10 while supplying pure water to the polishing surface plate 32, the agglomerated abrasive grains or fragments of the material to be polished adhered to the surface of the semiconductor substrate during the main polishing, or the buffing pad 30 are applied. Adhering particles and the like can be removed.

  Subsequently, the surface of the semiconductor substrate is pressed against the buffing pad 30 at a predetermined pressure, slurry containing abrasive grains is supplied from the slurry supply pipe 38 at a predetermined flow rate, and the polishing surface plate 32 and the polishing head 24 are rotated at a predetermined speed for a predetermined time. Slurry buffing is performed. Finally, pure water is supplied from the pure water supply pipe 36 at a predetermined flow rate, and buffing is similarly performed by rotating the polishing surface plate 32 and the polishing head 24 at a predetermined speed for a predetermined time.

  By performing slurry buff polishing, scratches generated on the surface of the semiconductor substrate during the main polishing can be removed, and the yield of the manufactured semiconductor device can be improved. By subsequent buffing with pure water, the surface of the semiconductor substrate can be washed to remove the slurry.

  Finally, the semiconductor wafer 10 after the buffing is finished is unloaded via the wafer unloader unit 18.

  When buffing is performed, the buffer step is not performed after the main polishing. At the time of buffing, the semiconductor wafer is mounted on the polishing surface plate 32 while supplying pure water, and the buffing is performed after the slurry buffing is performed. May be. Further, when the semiconductor substrate is detached from the buff polishing pad 30 during the buff polishing, a buffering step may be performed as in the main polishing.

  When the slurry is used at the time of main polishing as in the case of the above embodiment, the same slurry as at the time of main polishing can be used also at the time of buff polishing. If the amount of slurry supplied at the time of slurry buff polishing is too small, the effect of removing scratches cannot be obtained, and if too large, the slurry at the time of slurry buff polishing remains on the surface of the semiconductor substrate, causing a decrease in the yield of the semiconductor device. . Therefore, the amount of slurry supplied at the time of slurry buff polishing is preferably the same amount as at the time of main polishing, specifically, about ± 25% of that at the time of main polishing.

  As described in Patent Document 3, conventionally, when the slurry and pure water are mixed and the pH is changed, the agglomeration of abrasive grains occurs, which may cause scratches. However, in reality, even if the semiconductor substrate surface is mounted on the same buffing pad, it can be switched to pure water, slurry, or pure water, that is, the pure water and slurry are mixed at the timing of switching. It has been clarified that even if the state is changed, the scratches are not increased, but rather, the scratches generated by the main polishing can be reduced and the yield of the manufactured semiconductor device can be improved.

  Further, the specific polishing method of the surface of the semiconductor substrate is not limited at all. However, as a preferable example, the polishing pad 20 has a larger size than the semiconductor substrate as shown in FIG. The semiconductor substrate surface can be polished by rotating each of the semiconductor substrates around different axes. Further, the surface layer of the semiconductor substrate to be polished is not limited in any way, but as an example, a surface layer of an insulating film formed on the entire surface of the semiconductor substrate can be mentioned.

  As a CMP apparatus, AVECTI 472 manufactured by IPEC / WESTEC is used, as a polishing pad for main polishing, a two-layer pad of IC1000 / Suba-4, and as a buff polishing pad for buff polishing, Supreme RN-H is used. After polishing the surface of the semiconductor substrate on which the PSG film is deposited, use AIT-II manufactured by KLA-Tencor as a surface defect detection device, and the number of defects on the surface of the semiconductor substrate after polishing (observed by a defect inspection device). The number of scratches made was measured.

  In this embodiment, as shown in the graph of FIG. 2, the present invention is applied, a buffer step is performed after the main polishing, the semiconductor wafer is detached from the polishing pad, and only pure water is supplied. Buffing was performed. The vertical axis of the graph in FIG. 2 represents the pressure (psi) for pressing the semiconductor wafer against the polishing pad, and the horizontal axis represents the processing time (sec). T1, T2, Tt, and Tb represent a main polishing processing time, a buffer step processing time, a semiconductor wafer transfer time, and a buff polishing processing time, respectively.

  In addition, in order to confirm the effect of the buffer step, as before, after the main polishing, without performing the buffer step, the semiconductor wafer was detached from the polishing pad as it was, and buff polishing was performed by supplying only pure water. .

The processing conditions during main polishing were as follows.
Polishing platen rotational speed: 50 rpm
Polishing head rotation speed: 30 rpm
Pressure: 7 psi (4.8 × 10 ⁴ Pa)
The time was 60 seconds when the buffer step was not performed, and 55 seconds when the buffer step was performed.

The conditions during buffing were as follows.
Polishing platen rotational speed: 50 rpm
Polishing head rotation speed: 50 rpm
Pressure: 2 psi (1.4 × 10 ⁴ Pa)
Time: 30 seconds

The processing conditions during the buffering step were as shown in Table 1 below. That is, the rotation speed of the polishing platen / polishing head at the buffer step (relative speed between the semiconductor wafer and the polishing pad) was set to ½ of the rotation speed of the polishing platen / polishing head at the main polishing. The pressure at the buffering step was changed to a value equal to or lower than the pressure at the main polishing. That is, it was changed in the range of 7 psi (4.8 × 10 ⁴ Pa) to 1 psi (6.9 × 10 ³ Pa). In this experiment, the time was changed according to the pressure in order to compare with the same polishing amount in the buffer step. Table 1 shows numerical values obtained by normalizing the number of defects (pieces) on the entire surface of the 6-inch wafer by the polishing amount (nm) (hereinafter simply referred to as a standard value of the number of defects).

  As shown in Table 1, when the semiconductor wafer was detached without performing the buffering step, the standard value of the number of defects was 0.63 (pieces / nm). On the other hand, when the semiconductor wafer is detached after performing the buffering step, when the relative speed between the semiconductor substrate surface and the polishing pad is halved, the pressure is lowered to ½ or less and then detached (When the pressure was 3 psi and 1 psi), the standard value of the number of defects was increased. On the other hand, when the pressure is kept at 60% or higher and the relative speed is reduced to 1/2 and then desorption (when the pressure is 7 psi and 5 psi), the standard value of the number of defects is reduced. I was able to.

  FIG. 3 is a graph showing the relationship between the ratio P2 / P1 between the pressure P1 during main polishing and the pressure P2 during the buffering step, and the standard value for the number of defects, and the vertical axis indicates the standard for the number of defects. The value (pieces / nm) and the horizontal axis indicate the polishing pressure ratio P2 / P1. From this graph, if the standard value 0.63 of the number of defects when the buffering step is not performed is set as an upper limit, and a numerical value lower than this, for example, 0.5 is set as the target value of the standard value of the number of defects, this target value 0. It can be seen that the range in which the standard value of the number of defects is smaller than 5 is when the polishing pressure ratio P2 / P1 is about 0.60 or more.

  Using the same apparatus as in Example 1, the surface of the semiconductor substrate on which the PSG film was deposited was polished, and the number of defects on the surface of the semiconductor substrate after polishing was measured. In this embodiment, as shown in the graph of FIG. 4, the present invention is applied, and after the main polishing, the semiconductor wafer is detached from the polishing pad without performing a buffering step, and further supplied with pure water while supplying pure water. Was mounted on a polishing surface plate having a buffing pad (cleaning step), followed by slurry buffing, and finally boiled by supplying pure water. In the graph of FIG. 4, Ts represents the processing time of slurry buffing.

  In order to confirm the effect of slurry buff polishing, as before, after the main polishing, without performing the buffer step, the semiconductor wafer is detached from the polishing pad as it is, and then only pure water is supplied to perform buff polishing. It was. The buffing conditions are the same as in Example 1 whether or not slurry buffing is performed. The conditions for the main polishing are the same as in the case where the buffering step was not performed in Example 1 regardless of the presence or absence of slurry buffing.

  The processing conditions at the time of slurry buffing were as shown in Table 2 below. Table 2 also shows the difference between the polishing amount during slurry buff polishing, that is, the polishing amount when slurry buff polishing and buff polishing are performed, and the polishing amount when only buff polishing is performed.

  As shown in Table 2, when only buffing was performed, the number of defects was 38. On the other hand, when slurry buffing is performed, the number of defects is 32, 3, and 0 by slurry buffing for 15 seconds, 30 seconds, and 60 seconds, respectively, and the number of defects can be reliably reduced by slurry buffing. I was able to. Further, the polishing amounts at this time are 45 nm, 109 nm, and 261 nm, respectively, and it was found that the number of defects can be greatly reduced by slurry buffing of about 100 nm.

  Uses MIRRA manufactured by APPLIED MATERIALS as the CMP apparatus, uses IC1000 / Suba-4 two-layer pad as the polishing pad for main polishing, and Supply RN-H as the buff polishing pad for buff polishing, using BPSG The semiconductor substrate surface on which the film was deposited was polished.

  In this embodiment, as shown in the graph of FIG. 5, the present invention is applied, and after the main polishing, the semiconductor wafer is detached from the polishing pad, and then pure water is supplied to the polishing surface plate having the buff polishing pad. The semiconductor wafer was mounted (cleaning step) while being supplied, followed by slurry buff polishing, and further supplied with pure water for buff polishing.

  Further, in order to examine the difference in product yield depending on the presence or absence of slurry buffing, buffing was performed by supplying only pure water after main polishing as usual.

  The processing conditions in each processing were as shown in Table 3 below. The slurry flow rate during slurry buff polishing was 80% of the slurry flow rate during main polishing.

  As a result, the product yield was 82% when slurry buffing was not performed and only buffing with pure water was performed as usual. On the other hand, it was confirmed that the product yield improved to 87% when slurry buffing was performed by applying the present invention.

The present invention is basically as described above.
As mentioned above, although the manufacturing method of the semiconductor device of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, you may make various improvement and a change. Of course.

It is the schematic showing the process of grind | polishing the surface of a semiconductor wafer by applying the manufacturing method of the semiconductor device of this invention. 3 is a conceptual diagram illustrating a polishing process according to Example 1. FIG. It is a graph showing the relationship between the standard value of the number of defects, and polishing pressure ratio. 6 is a conceptual diagram illustrating a polishing process according to Example 2. FIG. 10 is a conceptual diagram illustrating a polishing process according to Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor wafer 11 CMP apparatus 12 Wafer loader part 14 Main polishing polishing unit 16 Buff polishing polishing unit 18 Wafer unloader part 20, 30 Polishing pad 22, 32 Polishing surface plate 24 Polishing head 26, 36 Pure water supply pipe 28, 38 Slurry supply pipe

Claims (6)

After polishing the semiconductor substrate surface by pressing the semiconductor substrate surface against the polishing pad with a predetermined pressure and moving the semiconductor substrate surface with respect to the polishing pad at a predetermined relative speed, the semiconductor substrate is When detaching from the polishing pad,
Removing the semiconductor substrate after performing a buffering step in which the pressing pressure against the polishing pad is kept within the range of 60% or more during the polishing and the relative speed is decreased as compared with the polishing. A method of manufacturing a semiconductor device.   2. The method of manufacturing a semiconductor device according to claim 1, wherein the relative speed in the buffering step is reduced to 2/3 to 1/3 of the relative speed during the polishing. After mounting the semiconductor substrate on a surface plate having a polishing pad and polishing the surface of the semiconductor substrate, when performing buffing by mounting on a surface plate having a buff polishing pad provided separately from the polishing pad,
The semiconductor substrate is mounted while supplying pure water to the surface plate having the buffing pad, and then slurry buffing is performed by supplying slurry containing abrasive grains, and then buffing is performed by supplying pure water. A method for manufacturing a semiconductor device, comprising: Polishing performed by attaching to the polishing pad is performed by supplying slurry containing abrasive grains to the polishing pad,
4. The semiconductor according to claim 3, wherein the slurry buff polishing is performed by supplying the same slurry as that supplied to the polishing pad at a supply rate in a range of ± 25% of the supply amount to the polishing pad. Device manufacturing method.   The polishing pad has a size larger than that of the semiconductor substrate, and the polishing surface of the semiconductor substrate is polished by rotating each of the polishing pad and the semiconductor substrate around different axes. The method for manufacturing a semiconductor device according to claim 1.   6. The method of manufacturing a semiconductor device according to claim 1, wherein the polishing of the surface of the semiconductor substrate is polishing of a surface layer of an insulating film formed on the entire surface of the semiconductor substrate.

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