CN114346893B - Chemical mechanical polishing method - Google Patents
Chemical mechanical polishing method Download PDFInfo
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- CN114346893B CN114346893B CN202210039252.XA CN202210039252A CN114346893B CN 114346893 B CN114346893 B CN 114346893B CN 202210039252 A CN202210039252 A CN 202210039252A CN 114346893 B CN114346893 B CN 114346893B
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Abstract
The invention provides a chemical mechanical polishing method, which comprises the following steps: the method comprises the steps of utilizing a chemical mechanical polishing device to polish a batch of wafers one by one, polishing at least two wafers, finishing a polishing pad of the chemical mechanical polishing device, generating polishing byproducts influencing the polishing rate in the process of carrying out chemical mechanical polishing on the wafers.
Description
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a chemical mechanical polishing method.
Background
In semiconductor manufacturing, with the upgrading of process technology and the shrinking of wire and gate dimensions, the requirement of photolithography (Non-uniformity) technology on the surface flatness of a wafer is increasing, and chemical mechanical polishing combines chemical etching and mechanical removal, so that global planarization can be realized in the current machining.
In a process of polishing a wafer with polysilicon (Poly CMP) using a soft polishing pad, byproducts generated during polishing contribute significantly to polishing rate, and when micropores in the polishing pad are sufficiently filled with polishing particles in a slurry and polishing byproducts generated during polishing, stability of the polishing rate is facilitated, and a function of adjusting the rigidity of the polishing pad is also performed, and when the filling of micropores in the polishing pad becomes unstable, polishing properties are also affected.
The dressing process of the polishing pad in the polysilicon chemical mechanical polishing (Poly CMP) process is performed independently of the polishing process, the dressing time does not change with the change of the polishing time, and a mode of dressing once and then polishing once is generally adopted. During the process of dressing the polishing pad, part of the filler on the surface of the polishing pad is cleaned, and the shape of the fluff layer on the surface of the polishing pad is improved. However, in the chemical mechanical polishing process of a part of the product, the polishing rate of the polysilicon is very high, the filling rate of the micropores in the polishing process is lower than the cleaning rate in the polishing pad trimming process, so that the number of the polishing particles and the polishing byproducts in the micropores is reduced, the polishing rate is gradually reduced, the thickness of the polished wafer is increased along with the increase of the number of wafers polished by the same polishing pad in the chemical mechanical polishing process, and the uniformity of the film thickness among the wafers subjected to chemical mechanical polishing is deteriorated.
Disclosure of Invention
The invention aims to provide a chemical mechanical polishing method which improves the uniformity of film thickness among wafers after a batch of wafers are polished by the same polishing pad.
In order to achieve the above object, the present invention provides a chemical mechanical polishing method, comprising:
and grinding a batch of wafers one by utilizing a chemical mechanical grinding device, and finishing a grinding pad of the chemical mechanical grinding device every grinding at least two wafers.
Optionally, the wafer includes a substrate and a gate structure on the substrate, and when the wafer is polished, a top portion of the gate structure of the wafer is polished.
Optionally, the polishing pad is conditioned at least once prior to polishing a first of the wafers.
Optionally, after polishing each wafer, measuring the thickness of the polished wafer, and if the thickness of the polished wafer is smaller than a preset value, trimming the polishing pad.
Optionally, the process of dressing the polishing pad and the process of polishing the wafer are independent of each other.
Optionally, the number of the wafers polished between two adjacent dressing steps is the same or different.
Optionally, the polishing pad is conditioned once or at least twice each time the polishing pad is conditioned.
Optionally, each dressing of the polishing pad is for the same time, and each dressing trims all of the polishing area of the polishing pad.
Optionally, the number of dressing times when dressing the polishing pad is positively correlated with the number of wafers polished after the polishing pad was last dressed.
Optionally, the polishing time of each wafer is the same.
The invention provides a chemical mechanical polishing method, which comprises the following steps: and grinding a batch of wafers one by utilizing a chemical mechanical grinding device, and finishing a grinding pad of the chemical mechanical grinding device every grinding at least two wafers. The invention adjusts the number of the wafers polished between every two trimmings in the chemical mechanical polishing process and the trimming times in each trimming process, adjusts the number of the polishing byproducts adhered on the polishing pad in the polishing process, further evenly grinds the wafers, and improves the uniformity of film thickness among wafers after chemical mechanical polishing is carried out on a batch of wafers.
Drawings
FIG. 1 is a schematic diagram of a chemical mechanical polishing apparatus according to an embodiment of the present invention;
FIG. 2 is a plot of polishing rate for continuous polishing;
FIG. 3 is a plot of thickness variation of the wafer after each polishing of one of the wafers while the polishing pad is being trimmed;
FIG. 4 is a schematic diagram of a chemical mechanical polishing method according to an embodiment of the present invention;
FIG. 5 is a plot of thickness variation of the wafer when the polishing pad is trimmed after each polishing of three wafers;
FIG. 6 is a plot of thickness variation of the polishing pad from a change in dressing the polishing pad after polishing three of the wafers to a change in dressing the polishing pad after polishing five of the wafers;
the drawings are as follows:
100-wafer; 102-a polishing pad; 104-a grinding head; 106, trimming the brush; 108-mechanical arm.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In the following, the terms "first," "second," and the like are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological order. It is to be understood that such terms so used are interchangeable under appropriate circumstances. Similarly, if the method described herein comprises a series of steps, and the steps presented herein are not necessarily the only order in which the steps may be performed, and some of the described steps may be omitted or some other steps not described herein may be added to the method.
The invention provides a chemical mechanical polishing method, which utilizes a chemical mechanical polishing device to polish a batch of wafers one by one, and fig. 1 is a schematic structural diagram of the chemical mechanical polishing device provided in this embodiment, as shown in fig. 1, the chemical mechanical polishing device comprises: a grinding unit and a slurry supply unit.
Specifically, the polishing unit includes a polishing pad 102 and a polishing head 104 for fixing and polishing a wafer 100, the wafer 100 is located between the polishing pad 102 and the polishing head 104, the diameter of the wafer 100 is smaller than or equal to the radius of the polishing pad 102, and the wafer 100 is located at one side of the polishing pad 102.
When the wafer 100 needs to be polished, the polishing head 104 drives the wafer 100 to move downwards, so that the surface to be polished of the wafer 100 contacts with the polishing pad 102, and the polishing slurry supply unit sprays polishing slurry containing polishing particles onto the surface of the polishing pad 102; in the process of polishing the wafer 100, the polishing head 104 continuously applies downward pressure to the wafer 100, so as to ensure that the surface of the wafer 100 is in close contact with the polishing pad 102, the polishing head 104 drives the wafer 100 to rotate, and the polishing pad 102 simultaneously rotates to polish the wafer 100.
The wafer 100 includes a substrate and a gate structure on the substrate, and when the wafer is polished, the top of the gate structure of the wafer is polished.
Further, the polishing pad 102 includes: the chassis, and the bonding layer and the nap layer sequentially located on the chassis, during the polishing process, the generated abrasive particles are bonded in the nap layer, and the abrasive particles are used for polishing the wafer 100. During the polishing of the wafer 100, polishing byproducts are continuously generated, and the adhesive layer adheres the polishing byproducts to the nap layer, and the polishing byproducts are continuously accumulated in the nap layer as polishing proceeds. The polishing byproducts and polishing particles may adjust the stiffness of the polishing pad 102. Fig. 2 is a graph showing polishing rate lines when continuous polishing is performed, and as shown in fig. 2, according to data of two tests, when a plurality of wafers are continuously polished by using the same polishing pad, the polishing rate of the wafers by the polishing pad increases with the number of the wafers continuously polished.
Since the polishing time for each wafer 100 is not changed, if the polishing byproducts and the polishing particles accumulated in the fluff layer are not cleaned, the polishing speed is higher, and the thickness of the wafer 100 after polishing is smaller, which affects the performance of the semiconductor device.
With continued reference to fig. 1, the cmp apparatus further includes a dressing unit, where the dressing unit includes a mechanical arm 108 and a dressing brush 106 disposed at one end of the mechanical arm 108. The conditioning brush 106 is used to remove a portion of the polishing particles and the polishing byproducts from the surface of the polishing pad 102 while conditioning the shape of the nap layer.
Wherein, the trimming brush 106 is a nylon brush, and the softer trimming brush 106 can better protect the fluff layer, thereby prolonging the service life of the polishing pad 102.
The process of dressing the polishing pad 102 by the dressing unit is performed separately from the process of polishing the wafer 100 by the polishing unit, and is independent of each other. Each time the polishing pad 102 is polished, the polishing brush 106 brushes the entire polishing area of the polishing pad 102 at least once, and each time the polishing is polished, the time for which the polishing is performed once is independent of the polishing process.
In the conventional cmp method, the polishing pad 102 is trimmed after polishing one wafer 100, but in the process of polishing the polysilicon layer, since the time for polishing the polysilicon layer is short, the number of the polishing byproducts accumulated in the polishing process of the fluff layer is small, if the manner of trimming is continuously performed after polishing each wafer, even if the number of trimming times in the trimming process is reduced to one, the number of the polishing byproducts removed in the trimming process is still larger than the number of the polishing byproducts accumulated in the fluff layer, and the number of the polishing byproducts in the fluff layer is continuously reduced along with the increase of the number of the wafers polished in the cmp process, so that the polishing rate of the wafer 100 is gradually reduced. Fig. 3 is a plot of thickness variation of the wafer when the polishing pad is polished after each wafer is polished, as shown in fig. 3, when the polishing time of each wafer is unchanged, the polishing pad is polished after each wafer is polished, and the thickness of the polished wafer is continuously increased with the increase of the number of the wafers polished by the polishing pad.
Fig. 4 is a schematic diagram of a chemical mechanical polishing method according to the present embodiment, and as shown in fig. 4, the present invention provides a chemical mechanical polishing method, including:
step S1: and grinding a batch of wafers one by utilizing a chemical mechanical grinding device, and finishing a grinding pad of the chemical mechanical grinding device every grinding at least two wafers.
By increasing the number of the wafers polished between two adjacent trimmings, the accumulated number of the polishing byproducts generated by polishing the wafers between two adjacent trimmings in the fluff layer is larger than or equal to the number of the polishing byproducts removed in each trimming process, so that the number of the polishing byproducts in the fluff layer is prevented from being reduced too much, and the thickness of each polished wafer is further uniform.
FIG. 5 is a graph showing a thickness variation line of the wafer when the polishing pad is polished every three wafers, as shown in FIG. 5, by using the method of polishing the polishing pad with three wafers every polishing, the thickness of the polished wafer fluctuates around a predetermined thickness with a smaller fluctuation range, and the absolute value of the difference between the thickness of the polished wafer and the predetermined thickness is smaller than
The thickness between the polished wafers has good uniformity.
Further, the polishing time for each wafer is the same, and the number of wafers polished between two adjacent polishing pads is the same or different, for example, three wafers are polished first to polish the polishing pad, and two wafers are polished to polish the polishing pad.
The dressing time of the polishing pad is the same each time, and all the polishing areas of the polishing pad are dressed each time. Each time the polishing pad is trimmed, it may be trimmed once or at least twice. The number of dressing times at each dressing of the polishing pad is positively correlated with the number of wafers polished after the polishing pad was last dressed, and thus, the polishing rate of the wafers can be adjusted by adjusting the number of dressing times at each dressing and the number of wafers polished between each dressing.
Fig. 6 is a thickness variation line diagram of the wafer when the polishing pad is trimmed from three wafers per polishing to five wafers per polishing, as shown in fig. 6, the polishing pad is trimmed from three wafers per polishing to five wafers per polishing, and the number of polishing sheets after each trimming is adjusted in real time according to the thickness of the wafers after polishing, so that the uniformity of the thickness between the polished wafers is better improved.
In addition, the polishing pad is conditioned at least once prior to polishing a first of the wafers. And (3) trimming the polishing pad before polishing, adjusting the shape of the fluff layer, and simultaneously removing dust and impurities on the surface of the polishing pad, so that the impurities on the surface of the polishing pad are prevented from scratching the surface of the wafer, and unnecessary loss is avoided.
In other alternative embodiments, the thickness of each polished wafer may be measured after polishing each wafer, and the polishing pad may be trimmed when the thickness of each polished wafer is less than a predetermined value. And measuring the thickness of the polished wafer in real time, judging whether the polishing pad is trimmed according to the size relation between the polished thickness of the wafer and a preset value, eliminating the influence of individual difference of the wafer, and simultaneously avoiding the thickness of the polished wafer from being too thin.
In summary, the present invention provides a chemical mechanical polishing method, comprising: and grinding a batch of wafers one by utilizing a chemical mechanical grinding device, and finishing a grinding pad of the chemical mechanical grinding device every grinding at least two wafers. The invention adjusts the number of the wafers polished between every two dressing processes and the dressing times in each dressing process by adjusting the number of the polishing byproducts adhered on the polishing pad in the polishing process and the number of the polishing byproducts removed from the polishing pad in the dressing process, thereby evenly polishing the wafers and improving the uniformity of film thickness among wafers after a batch of wafers are polished.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art will make any equivalent substitution or modification to the technical solution and technical content disclosed in the invention without departing from the scope of the technical solution of the invention, and the technical solution of the invention is not departing from the scope of the invention.
Claims (8)
1. A method of chemical mechanical polishing, comprising:
polysilicon grinding is carried out on a batch of wafers one by utilizing a chemical mechanical grinding device, at least two wafers are ground, and a grinding pad of the chemical mechanical grinding device is trimmed, so that the accumulated quantity of grinding byproducts generated by grinding the wafers between two adjacent trimmings in a fluff layer in the grinding pad is greater than or equal to the quantity of grinding byproducts cleared in each trimming process;
and after finishing grinding each wafer, measuring the thickness of the ground wafer, and if the thickness of the ground wafer is smaller than a preset value, finishing the grinding pad, wherein the process of finishing the grinding pad and the process of grinding the wafer are mutually independent.
2. The method of claim 1, wherein the wafer comprises a substrate and a gate structure on the substrate, and wherein the polishing of the wafer is performed on top of the gate structure of the wafer.
3. A chemical mechanical polishing method as recited in claim 1, wherein said polishing pad is conditioned at least once prior to polishing a first one of said wafers.
4. The method of claim 1, wherein the number of wafers polished between two adjacent dressing steps is the same or different.
5. The method of claim 4, wherein the polishing pad is dressed once or at least twice each time the pad is dressed.
6. The method of claim 5, wherein each dressing is performed for the same time and each dressing is performed for all of the polishing area of the polishing pad.
7. The method of claim 5, wherein the number of dressing steps performed each time the polishing pad is dressed is positively correlated with the number of wafers polished after the polishing pad was last dressed.
8. The method of claim 1, wherein the polishing time is the same for each wafer.
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| CN202210039252.XA CN114346893B (en) | 2022-01-13 | 2022-01-13 | Chemical mechanical polishing method |
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| CN202210039252.XA CN114346893B (en) | 2022-01-13 | 2022-01-13 | Chemical mechanical polishing method |
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| CN114346893B true CN114346893B (en) | 2023-06-30 |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10315131A (en) * | 1997-05-23 | 1998-12-02 | Hitachi Ltd | Polishing method of semiconductor wafer and device therefor |
| JP2001088008A (en) * | 1999-09-16 | 2001-04-03 | Toshiba Corp | Polishing method and device |
| JP2002052459A (en) * | 2000-08-09 | 2002-02-19 | Hitachi Ltd | Polishing method and polishing device |
| CN102452039A (en) * | 2010-10-19 | 2012-05-16 | 上海宏力半导体制造有限公司 | Chemical-mechanical grinding method |
| CN102672598A (en) * | 2012-05-22 | 2012-09-19 | 上海宏力半导体制造有限公司 | Grinding pad using method and wafer grinding method |
| CN105364699A (en) * | 2014-07-25 | 2016-03-02 | 中芯国际集成电路制造(上海)有限公司 | A chemical mechanical polishing method and a chemical mechanical polishing apparatus |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003151934A (en) * | 2001-11-15 | 2003-05-23 | Seiko Epson Corp | Cmp system and method of adjusting polishing pad for cmp |
| CN105328562A (en) * | 2014-07-16 | 2016-02-17 | 中芯国际集成电路制造(上海)有限公司 | Chemical and mechanical grinding method |
| CN107914213B (en) * | 2016-10-10 | 2020-06-05 | 中芯国际集成电路制造(上海)有限公司 | Chemical mechanical polishing method |
| CN110549239A (en) * | 2018-05-31 | 2019-12-10 | 长鑫存储技术有限公司 | Chemical mechanical polishing device and polishing pad surface dressing method |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10315131A (en) * | 1997-05-23 | 1998-12-02 | Hitachi Ltd | Polishing method of semiconductor wafer and device therefor |
| JP2001088008A (en) * | 1999-09-16 | 2001-04-03 | Toshiba Corp | Polishing method and device |
| JP2002052459A (en) * | 2000-08-09 | 2002-02-19 | Hitachi Ltd | Polishing method and polishing device |
| CN102452039A (en) * | 2010-10-19 | 2012-05-16 | 上海宏力半导体制造有限公司 | Chemical-mechanical grinding method |
| CN102672598A (en) * | 2012-05-22 | 2012-09-19 | 上海宏力半导体制造有限公司 | Grinding pad using method and wafer grinding method |
| CN105364699A (en) * | 2014-07-25 | 2016-03-02 | 中芯国际集成电路制造(上海)有限公司 | A chemical mechanical polishing method and a chemical mechanical polishing apparatus |
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| CN114346893A (en) | 2022-04-15 |
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