JP3187162B2 - Polishing device and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and a semiconductor device, and more particularly, to a polishing apparatus and a semiconductor device for flattening a wafer surface on which a wiring layer and a covering insulating film are formed.

[0002]

2. Description of the Related Art FIGS. 7 (a) and 7 (b) are structural views of a conventional polishing apparatus, and FIGS. 8 (a) to 8 (c) are cross-sectional views for explaining a conventional polishing method.

In FIGS. 7 (a) and 7 (b), reference numeral 1 denotes a rotatable disk-shaped platen, 2 denotes a polishing cloth stuck on the platen 1, and 3 denotes a plate facing the platen 1. A disk-shaped wafer holder for fixing the wafer 5 on which the wiring layer and the coating insulating film as the object to be polished are formed, and which is smaller than the diameter of the platen 1;
The platen 1 rotates in the same direction as the rotation direction. Reference numeral 4 denotes a nozzle for dropping an abrasive containing colloidal silica.

A method of polishing using the above polishing apparatus will be described with reference to FIGS. 8 (a) to 8 (c). FIG. 8A is a cross-sectional view of a wafer showing a state after a wiring layer and a covering insulating film are formed and before polishing, wherein 6 is a semiconductor substrate, and 7 is a base insulating film on the semiconductor substrate 6. , 8 are lower wiring layers formed on the underlying insulating film 7, 9 a and 9 b are columnar connection conductors for connecting the lower wiring layer 8 to an upper wiring layer to be formed later, Are formed in two places. 10 is a lower wiring layer 8 and a connecting conductor 9a,
9b is an interlayer insulating film that covers 9b.

In such a state, first, the wafer 5 is held on the wafer holder 3 shown in FIG. 7A so that the surface on which the lower wiring layer 8 and the interlayer insulating film 10 are formed becomes a polished surface. , Fix. Next, the lower wiring layer 8 and the interlayer insulating film 1
After the wafer holder 3 and the platen 1 on which the polishing cloth 2 is attached are opposed to each other so that the surface on which the polishing pad 2 is formed and the surface of the polishing pad 2 face in parallel, the wafer holder 3 and the platen The wafer holder 3 is moved downward while rotating the wafer holder 1 in the same direction, and the abrasive is dropped from the nozzle 4 onto the polishing pad 2.

[0006] The wafer holder 3 is pressed to
Are appropriately moved on the surface plate 1, while the connection conductors 9a,
The interlayer insulating film 10 on the wafer 5 is polished until 9b is exposed. After a lapse of a predetermined time, the interlayer insulating film 10 is polished, the surface of the wafer 5 is flattened, and the connection conductors 9a and 9b are exposed (FIG. 8B).

After that, when the upper wiring layers 11a and 11b are formed by connecting to the exposed connecting conductors 9a and 9b, the lower wiring layer 8 and the upper wiring layers 11a and 11a are connected via the connecting conductors 9a and 9b.
11b is connected (FIG. 8 (c)).

[0008]

However, according to the above-described conventional polishing method, the amount of polishing varies within the surface of the wafer 5 due to the degree of force applied to the wafer holder 3 during polishing. The same interlayer insulating film 1 throughout the plane
It is difficult to obtain a residual film thickness of 0. Therefore, FIG.
As shown in (1), there is a problem that the film thickness of the remaining connection conductors 9a and 9b and the interlayer insulating film 10a becomes thin, and the breakdown voltage of the insulating film between the upper and lower wiring layers is reduced and a short circuit occurs between the upper and lower wiring layers.

In order to solve this problem, it is only necessary to observe the polished surface of the wafer during polishing. However, it is necessary to perform a cleaning process on the wafer, observe with a microscope, or the like, which causes a decrease in throughput. The present invention has been made in view of the problems of the related art, and provides a polishing apparatus and a semiconductor device capable of uniformly polishing the inside of a wafer without observing the wafer polishing surface during polishing. It is intended for.

[0010]

SUMMARY OF THE INVENTION The first object of the present invention is to firstly provide a rotatable platen, a first conductive film on the platen,
A polishing cloth on the first conductive film having an opening formed so that the conductive film is exposed, and a second conductive film formed on a holding surface of the wafer, wherein the holding surface has the polishing surface. A rotatable wafer holder, which is arranged to face a cloth and contacts the wafer on the holding surface with the polishing cloth by moving the surface plate or by moving itself, and polishing the wafer by polishing; This is achieved by a polishing apparatus having a nozzle for discharging an agent and a power supply connected to the first conductor film and the second conductor film via current detection means, and secondly, a direct contact with the semiconductor substrate. And a plurality of current conducting portions made of a conductor having a height equal to the remaining film thickness of the object to be polished are formed, and a cross-sectional area of the plurality of current conducting portions is a reference current passing portion. X ⁿ times the cross-sectional area of the part (x ≧ 2, n is an integer)
This is achieved by a semiconductor device characterized by the following.

[0011]

In the polishing apparatus of the present invention, a first conductive film is formed on a surface plate, and a polishing cloth having an opening through which the first conductive film is exposed is formed thereon. In addition, a second conductive film is formed on a holding surface of the wafer holder facing the surface plate. Further, the first conductive film and the second conductive film are discharged via a nozzle for discharging an abrasive containing ions, and a current detecting means.
And a power supply connected to the conductive film.

Further, the semiconductor device of the present invention has a current flow portion made of a conductor which is in direct contact with the semiconductor substrate and has a height equal to the thickness of the polished body to be polished. are doing. In particular, ^assuming that the cross-sectional area of the current flow portion is ^xn times (x ≧ 2, n is an integer) with respect to the cross-sectional area of the reference current flow portion, any of the plurality of current flow portions is energized. Different values are always obtained. For example, when x = 2, n = 1, 2, 2, with respect to the cross-sectional area 1 of the reference current flow portion.
2, 4, 8, 16,... Corresponding to 3, 4,.
It becomes the relationship.

Therefore, when polishing an interlayer insulating film or the like covering a wiring layer or the like on the surface of the wafer, the wafer is held on the second conductor film of the wafer holder, and the first conductor on the surface plate is polished. The polishing cloth on the film is brought into contact with the wafer and pressed to polish. When any one of the current flow portions on the wafer is exposed, ions in the wafer abrasive that have entered the opening provided in the polishing pad intervene, so that the first conductive film / ion / The first path on the surface plate through the object to be polished by the current path of the current conducting portion / semiconductor substrate / second conductive film.
An electric current flows between the conductive film of the wafer holder and the second conductive film of the wafer holder. Therefore, by polishing while monitoring this current, the current flowing portion where current does not flow and the peripheral portion corresponding to the portion where the remaining film thickness is larger than the predetermined film thickness and the peripheral portion thereof are specified. By increasing the pressing force, the polishing amount can be increased.

As described above, since the polishing amount can be partially adjusted while monitoring the current, it is not necessary to observe the wafer surface during polishing as in the related art. Thereby, the process can be simplified and more uniform polishing can be performed.

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. (1) Polishing Apparatus of First Embodiment of the Present Invention FIGS. 1A and 1B are configuration diagrams of a polishing apparatus according to a first embodiment of the present invention.

In FIGS. 1 (a) and 1 (b), reference numeral 21 denotes a rotatable disk-shaped surface plate on which a first conductive film 22 is formed. Reference numeral 23 denotes a polishing cloth adhered on the first conductive film 22, and a large number of small openings 24 are formed. The first conductive film 22 is exposed at the bottom of the opening 24. Reference numeral 25 denotes a wafer 3 which is provided opposite to the surface plate 21 and has a lower wiring layer and a coating insulating film as a body to be polished.
This is a disc-shaped wafer holder for fixing 0, which is smaller than the diameter of the platen 21 and rotates. Further, a second conductor film 26 is formed on the surface of the wafer holder 25. 27 is a nozzle for dropping an abrasive containing ions, for example, colloidal silica containing Na ions and K ions,
Reference numeral 28 denotes a power supply for supplying a voltage, which is connected to the first conductive film 22 of the surface plate 21 and the second conductive film 26 of the wafer holder 25 via an ammeter (current detecting means) 29. .

As described above, according to the polishing apparatus of the first embodiment of the present invention, the first conductor film 22 and the second conductor film 26 are formed on the surfaces of the surface plate 21 and the wafer holder 25, respectively. An opening 24 is formed in the polishing pad 23 on the first conductive film 22 of the platen 21, and a nozzle 27 into which an abrasive containing ions is dropped.

Accordingly, when the wafer 30 is held by the wafer holder 25 and the interlayer insulating film covering the lower wiring layer on the surface of the wafer 30 is polished, the first conductive film 2 on the surface plate 21 is polished.
The polishing cloth 23 on the wafer 2 and the wafer 30 on the second conductive film 26 on the wafer holder 25 are brought into contact with each other, pressed and polished, and any one of the current passing portions 32a to 32d on the wafer 30 is polished. When the ions appear in the polishing agent that has entered the opening 24 when the first conductive film 22 /
Ion / current flow part 32a-32d / semiconductor substrate 31 / second
A current can flow between the first conductive film 22 on the bottom platen 21 and the second conductive film 26 on the wafer holder 25 via the conductive film 26 of FIG.

As a result, the polishing can be performed while monitoring the current, so that it is not necessary to observe the wafer surface during polishing as in the prior art. The process can be simplified and more uniform polishing can be performed.

(2) Semiconductor Device of Second Embodiment of the Present Invention FIGS. 2A and 2B are explanatory views of a semiconductor device according to a second embodiment of the present invention. Is a top view of the wafer, and FIG. 2B is a sectional view of the wafer.

2 (a) and 2 (b), reference numeral 31 denotes a semiconductor substrate made of, for example, silicon;
0 at the center (C) and 4 at the periphery (A, B,
D, E) formed by a column-shaped tungsten (W) film current flow portion, which is directly connected to the semiconductor substrate 31 at the bottom of the opening of the base insulating film 33, and has a cross-sectional area of A The current flowing portions 32b to 32d of the B, C, D, and E portions are 2, 4, 8, and 16, respectively, with respect to one of the current flowing portions 32a of the portion. The cross-sectional areas are set to 1, 2, 4, 8, and 16 because the current conducting portions are specified so that different values are always obtained even when a plurality of current conducting portions are conducted. It is.

For example, when polishing the interlayer insulating film covering the lower wiring layer on the surface of the wafer 30, the surface plate 21 and the wafer 30 on the wafer holder 25 are brought into contact with each other and polished. When any of the flow portions 32a to 32d is exposed, the ions in the wafer abrasive that have entered the opening 24 are interposed, so that the first conductive film 22 / ion / current flow portions 32a to 32d are exposed. A current flows between the first conductive film 22 of the bottom platen 21 and the second conductive film 26 of the wafer holder 25 via the 32d / semiconductor substrate 31 / second conductive film 26.

(3) Polishing method of the third embodiment of the present invention FIGS. 3 (a), 3 (b), and 3 (b) show the polishing method of the second embodiment of the present invention in which the above-mentioned polishing apparatus is used for polishing. 4 (a)
-(C) and FIGS. 1 (a), (b), 2 (a), (b)
This will be described with reference to FIG. 3 (a) and 3 (b) are diagrams showing changes with time in the current flowing through the ammeter, and FIGS. 4 (a) to 4 (c).
FIG. 3 is a cross-sectional view illustrating a method for manufacturing a semiconductor device including the polishing method according to the embodiment.

FIG. 4A is a cross-sectional view of a wafer showing a state after a lower wiring layer and a covering insulating film are formed and before polishing, and reference numeral 31 denotes a semiconductor substrate made of silicon;
Reference numeral 3 denotes a base insulating film made of a silicon oxide film on the semiconductor substrate 31, reference numeral 34 denotes a lower wiring layer (conductor layer) made of aluminum formed on the base insulating film 33, and reference numerals 35a and 35b denote a lower wiring layer 34 to be formed later. A connection conductor made of columnar aluminum for connecting to the upper wiring layer to be formed, and is formed at two places on the lower wiring layer 34. Reference numeral 36 denotes an interlayer insulating film (insulating film) made of a silicon oxide film that covers the lower wiring layer 34 and the connection conductors 35a and 35b.

In this state, first, the wafer 30 is held on the wafer holder 25 shown in FIG. 1A so that the surface on which the lower wiring layer 34 and the interlayer insulating film 36 are formed is exposed. Fix it. Next, the wafer holder 25 and the surface plate 21 on which the polishing pad 23 is adhered face each other so that the surface on which the lower wiring layer 34 and the interlayer insulating film 36 are formed faces the surface of the polishing pad 23 in parallel. Then, while rotating the wafer holder 25 and the surface plate 21 in the same direction, the wafer holder 25
Is moved downward or the surface plate 21 is moved upward to make contact therewith, and the abrasive is dropped from the nozzle 27 onto the polishing pad 23.

While pressing the wafer holder 25 and moving the wafer holder 25 on the surface plate 21 appropriately, the wafer 30
The upper interlayer insulating film 36 is polished. At this time, the ammeter 29
To monitor. Now, polishing has progressed to some extent, and the current
Assuming that b is exposed, at this time, a current corresponding to the cross-sectional area 2 flows and is detected by the ammeter 29. Therefore, parts other than the part B are pressed relatively strongly. Polishing proceeds, then
Assuming that the current flow portion 32e is exposed, a current corresponding to the cross-sectional area 2 + 16 flows and is detected by the ammeter 29. Therefore, parts other than the part B and the part E are pressed relatively strongly. Assuming that the polishing proceeds, and then the current flow portion 32a is exposed,
A current corresponding to the cross-sectional area 2 + 16 + 1 flows, and the ammeter 29
Is detected. Therefore, parts other than the B part, the E part and the A part are pressed relatively strongly. Assuming that the polishing proceeds and then the current flow portion 32c is exposed, a current corresponding to a cross-sectional area of 2 + 16 + 1 + 4 flows and is detected by the ammeter 29. Therefore, the periphery of the portion D other than the portions B, E, A and C is pressed relatively strongly. Assuming that the polishing progresses and then the current flow portion 32d is exposed, a current corresponding to a cross-sectional area of 2 + 16 + 1 + 4 + 8 flows and is detected by the ammeter 29. This allows
It is determined that all of the current flow portions 32a to 32e are conductive and a predetermined polishing amount has been achieved, and polishing is terminated (FIG. 3).
(A)). In the case of FIG. 3B, first, the current flow portion 32b of the portion B conducts, and thereafter, the current flow portions 32a, 32c to 32c.
e indicate that they are conducting simultaneously.

As a result, as shown in FIG. 5, a predetermined amount of the interlayer insulating film 36 is uniformly polished over the entire surface of the wafer 30, and the surface of the wafer 30 is flattened. Then, the connecting conductors 35a and 35b are exposed (FIG. 4B).

Thereafter, when the upper wiring layers 37a and 37b are formed by connecting to the exposed connection conductors 35a and 35b, the lower wiring layer 34 and the upper wiring layer 37 are connected via the connection conductors 35a and 35b.
a and 37b are connected (FIG. 4C).

The variation in the remaining film thickness of the interlayer insulating film 36a on the wafer 30 formed as described above in the wafer 30 and the average remaining film thickness between the wafers 30 were examined. The results are shown in FIGS. 6A and 6B, respectively.

According to the results of the above investigation, both the variation in the remaining film thickness in the wafer and the variation in the average remaining film thickness between the wafers were significantly improved as compared with the conventional example. As described above, according to the present invention, it is possible to check the polishing amount of each part of the wafer while monitoring the ammeter 29. Therefore, the polishing amount can be made uniform by adjusting the pressing force of the necessary portion. . As a result, the variation in the remaining film thickness of the interlayer insulating film 36a after polishing in the wafer 30 and the variation in the average remaining film thickness between the wafers 30 can be significantly improved as compared with the conventional example. The process can be simplified by obviating the need for wafer observation on the way.

[0031]

As described above, in the polishing apparatus of the present invention, the first conductive film is formed on the surface plate, and the polishing cloth having the opening through which the first conductive film is exposed is formed thereon. And a second conductive film is formed on the holding surface of the wafer holder facing the surface plate. Further, it has a nozzle for discharging a polishing agent containing ions, and a power supply connected to the first conductor film and the second conductor film via current detection means.

Further, the semiconductor device of the present invention has a current flow portion made of a conductor which is in direct contact with the semiconductor substrate and has a height equal to the thickness of the polished body to be polished to remain. are doing. In particular, by making the cross-sectional area of the current flow portion ^xn times (x ≧ 2, n is an integer) the cross-sectional area of the reference current flow portion, an arbitrary plurality of current flow portions can be energized. However, a different value is always obtained, and a non-conductive current flow portion can be specified.

Therefore, when polishing an interlayer insulating film or the like covering a wiring layer or the like on the surface of the wafer, the wafer is held on the second conductive film of the wafer holder, and the first conductive film on the surface plate is polished. The polishing cloth on the film is brought into contact with and pressed against the wafer, and the polishing is performed while monitoring the current flowing between the first conductive film and the second conductive film. It is possible to specify a current flowing portion and a peripheral portion thereof that are not flowing, that is, a portion where the remaining film thickness is larger than a predetermined film thickness, and increase the pressing force of the portion to increase the polishing amount.

As described above, since the polishing amount can be partially adjusted while monitoring the current, it is not necessary to observe the wafer surface during polishing as in the related art. Thereby, the process can be simplified and more uniform polishing can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a polishing apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a semiconductor device according to a second example of the present invention.

FIG. 3 is an explanatory diagram of a change over time of a monitoring current by a polishing method according to a third embodiment of the present invention.

FIG. 4 is a sectional view illustrating a method for manufacturing a semiconductor device including a polishing method according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating flatness of a wafer surface obtained by a polishing method according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing the results of a survey on the variation in the remaining film thickness in a wafer of the remaining film obtained by the polishing method according to the third embodiment of the present invention and the average remaining film thickness between wafers.

FIG. 7 is a configuration diagram of a polishing apparatus according to a conventional example.

FIG. 8 is a cross-sectional view illustrating a method of manufacturing a semiconductor device including a polishing method according to a conventional example.

FIG. 9 is a cross-sectional view illustrating flatness of a wafer surface obtained by a polishing method according to a conventional example.

[Explanation of symbols]

 Reference Signs List 21 surface plate, 22 first conductive film, 23 polishing cloth, 24 opening, 25 wafer holder, 26 second conductive film, 27 nozzle, 28 power supply, 29 ammeter (current detecting means), 30 wafer 31 semiconductor substrate, 32a-32d current flow section, 33 base insulating film, 34 lower wiring layer (conductor layer), 35a, 35b connecting conductor, 36, 36a interlayer insulating film (insulating film), 37a, 37b upper part Wiring layer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Bunri Sugimoto 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-61-8943 (JP, A) JP-A-1- 207929 (JP, A) JP-A-3-97226 (JP, A) JP-A-55-54174 (JP, A) JP-A-3-174740 (JP, A) JP-A-4-261773 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/304 621 H01L 21/304 622 H01L 21/3205 B24B 37/00 B24B 37/04

Claims (2)

(57) [Claims] 1. A rotatable surface plate, a first conductor film on the surface plate, and the first conductor having an opening formed to expose the first conductor film. A second conductive film is formed on the polishing cloth on the film and the holding surface of the wafer, and the holding surface is disposed so as to face the polishing cloth, and the holding surface is moved by the movement of the platen or by itself. A rotatable wafer holder for bringing the upper wafer into contact with the polishing cloth and polishing the wafer, a nozzle for discharging a polishing agent containing ions, and the first conductive film and the A polishing apparatus having a power supply connected to the second conductive film. 2. A method according to claim 1, further comprising: forming a plurality of current flow portions made of a conductor which is in direct contact with the semiconductor substrate and has a height equal to the remaining film thickness of the object to be polished; A semiconductor device, wherein a cross-sectional area is ^xn times (x ≧ 2, n is an integer) times a cross-sectional area of a reference current flow portion.