JP2001009699A - Plane surface grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane surface grinding device capable of flatly grinding a wafer by a required amount. SOLUTION: During grinding a wafer 10 wherein some kinds of material are laminated, through singular light transparent window WT provided on a platen 11, the amount of reflecting light from a ground surface of the wafer 10 is detected by a light detector 29 at the all time, and is detected by a plurality of light sensors Sn during a plurality of light transparent windows Wn passes through a bottom surface of the wafer 10. On the bases of the light amount, pressing force of plural pressurizing chambers provided on every ring- shaped areas within a head portion 14 is controlled, and pressing force on the wafer 10 is suitably set for each ring-shaped area to grind.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar polishing apparatus, and more particularly, to a planar polishing apparatus for polishing a surface of a semiconductor wafer (hereinafter, referred to as a wafer) to a flat and mirror surface.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, circuit wiring has become finer and the distance between wirings has become smaller. One example of the manufacturing process of the wafer in it,
This will be described with reference to the cross-sectional view of the wafer shown in FIG.

[0003] A barrier metal layer 2 (for example, Ta) is formed on the surface of the underlying silicon 1 which has been grooved by etching or the like.
N) and the wiring material layer 3 (for example, Cu) are sequentially laminated by sputtering or the like (FIG. 11A), and then the wiring material layer 3 is removed so as to remain only in the groove, thereby forming the wiring remaining in the groove. The material layer 3 becomes the wiring of the circuit, and the wiring with a narrow pitch is formed on the wafer (FIG. 11B). At this time, it is necessary to make the cross-sectional areas of the wirings uniform so that the electric resistances do not greatly differ from each other, to make the depths uniform, and to suppress the generation (dishing) of the wiring portion 4 surface (polished surface). There is. (See FIG. 12 (a))

As a method for removing the barrier metal layer 2 and the wiring material layer 3 on the wafer surface, polishing is used. Conventionally, a planar polishing apparatus of this type has a platen and a head section that rotate at independent rotation speeds, the head section applies a constant pressure to the platen, and a polishing pad containing slurry on the platen and a head section. Then, the wafer is sandwiched between them, and while holding the wafer, a slurry is interposed between the polishing pad and the wafer for polishing for a certain time.

[0005] The performance of the above-mentioned planar polishing apparatus includes not only the high-precision flatness of the polished wafer but also the removal of only the barrier metal layer 2 and the wiring material layer 3 on the wafer surface.
Since the groove in which the wiring material layer 3 is embedded must be left at a certain depth, it is required that the polishing amount itself can be controlled with high accuracy.

Among them, in order to improve the flatness of the wafer, a holding surface for holding a semiconductor wafer during polishing, that is, a lower end surface of a head portion, a contact surface of a polishing pad in contact with the semiconductor wafer, and a polishing pad of a platen The surface having a high degree of flatness with high accuracy has been used for the surface to which the semiconductor wafer is attached, and a device for adjusting the distribution of the pressing force on the polished surface of the semiconductor wafer has been devised.

As one of the devices for adjusting the distribution of the pressing force on the polishing surface, there is a structure of a head portion as shown in FIG. The head section has two independent annular air chambers, each of which has a plurality of openings 5 formed in the wafer holding surface. This is to prevent the polishing liquid from entering the central portion of the wafer when the wafer is polished, thereby preventing the amount of polishing at the central portion of the wafer from decreasing. The above problem is prevented by supplying compressed air having a higher pressure to the air chamber at the center portion during polishing than the air chamber at the peripheral portion.

[0008]

However, even if the flatness of the polished wafer is improved by polishing the wafer using the head having the above-described structure, the polishing amount cannot be controlled. The thickness of the wiring material layer 3 may also vary between wafers and between lots in the previous manufacturing process, and if the wiring material layer 3 is thickly stacked in some cases, it is only necessary to grind for a certain period of time under certain conditions. There is a problem that the wiring material layer 3 or the barrier metal layer 2 remains on the wafer surface without being removed, and a wiring pattern is not formed on the wafer surface.

On the other hand, if the polishing is performed for a long period of time because the wiring material layer 3 or the barrier metal layer 2 is not removed and remains on the wafer surface without being removed, the underlying silicon 1 is removed after the barrier metal layer 2 is removed. As a result, the surface of the wiring portion 4 is continuously polished for a long time, and as a result, the surface of the wiring portion 4 made of Cu, which is more easily polished than silicon, sags (dishing), and the electric resistance of each wiring varies. Was. (See FIG. 12 (a))

Furthermore, even if a wafer is polished for a certain period of time under a certain condition using the head having the above-described structure, the appropriate value of the pressure of the compressed air supplied to each air chamber is determined by the number of times performed so far. It must be empirically predicted and set based on the polishing result, and it is impossible to determine or change an appropriate value for the wafer currently being polished in real time. For this reason, the wafer surface after polishing is often not flat, the periphery of the wafer is polished more, and the wiring groove depth at the periphery becomes shallower than the inner periphery (thinning). In addition, the electric resistance of each wiring is to be varied. (See FIG. 12B)

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a planar polishing apparatus which can polish a wafer flat and a desired amount.

[0012]

In order to achieve the above-mentioned object, the present invention provides a platen having a polishing pad attached to an upper surface thereof, and a head portion above the platen. The platen and the head rotate while applying a predetermined pressure across the object to be polished, and the object to be polished is polished by interposing a slurry between the polishing pad and the object to be polished. A pressurized fluid can be ejected to the surface holding the object, a plurality of opening holes are provided in a plurality of concentric annular regions divided into the head portion, and the pressurized fluid can be supplied to each of the regions. The platen has a single light transmission window penetrating with a polishing pad attached to the upper surface, a light transmission material is fitted into the light transmission window, and the lower surface of the platen has the single light transmission material. Light transmission window area and platen A reflection mirror is attached to the rotation center and a reflection mirror attached to the lower surface of the rotation center of the platen.In a plane polishing apparatus having a light source and a photodetector below the reflection mirror, the light emitted from the light source is 2
The light is projected on the object to be polished through the single light transmission window through the reflecting mirrors, and is reflected light from the object to be polished, and the light returned by the same path is received according to the amount of light received by the photodetector. And a control unit capable of changing the pressure of the pressurized fluid for each of the regions.

Further, the present invention has a platen having a polishing pad attached to an upper surface thereof, and a head portion above the platen.
The platen and the head rotate while applying a predetermined pressure to the object to be polished between the platen and the head, and the object to be polished is polished by interposing a slurry between the polishing pad and the object to be polished. A pressurized fluid can be ejected to the surface where the head section holds the object to be polished, and a plurality of opening holes are provided in a plurality of concentric annular areas divided into the head section, and each of the areas has In a planar polishing apparatus capable of supplying a pressurized fluid, the platen has a plurality of light transmitting windows penetrating therewith along with a polishing pad attached to an upper surface, and the plurality of light transmitting windows transmit light. A mold material is fitted therein, and a plurality of optical sensors are arranged below the platen.

Here, when the center of the object to be polished is placed at the midpoint of a concentric line segment on which the plurality of optical sensors are disposed, any of the optical sensors is used. The platens are provided at equal intervals in a range that does not protrude from the object to be polished, and are arranged on a line in which a concentric circle of the platen that passes through the center of rotation of the head portion is translated downward. On the other hand, the number of the plurality of light transmitting windows is the same as that of the optical sensors, and all the light transmitting windows have a positional relationship that coincides directly above all the optical sensors.

The optical sensor receives light that is projected from the optical sensor onto the object to be polished and becomes reflected light from the object to be polished, and receives the light by the optical sensor. The pressure of each can be changed, during polishing, with the rotation of the platen, the plurality of light transmission windows from the polishing target obtained when passing directly above each of the plurality of optical sensors. The plurality of optical sensors all store the reflected light reception amount, and during the passage of the polishing object, the number of reflections received by each optical sensor equal to the number of the plurality of light transmission windows, The average value of the sum of values obtained by removing abnormal values from the stored reflected light reception amounts is characterized.

Further, the present invention has both of the above-described two types of configurations and a control unit, and a single light transmitting window penetrating with the polishing pad attached to the upper surface of the platen includes:
A plurality of light transmission windows also provided on the platen pass through the rotation center on a line passing from the midpoint of a line segment on the concentric circle of the platen disposed thereon to the rotation center of the platen. Placed at

As a result, during the polishing, the two controls are sequentially performed according to the rotation of the platen, and the pressure of the pressurized fluid can be changed for each of the regions twice in total during one rotation of the platen. It is a feature.

[0018]

The planar polishing apparatus of the present invention has the above-described configuration.
First, on the platen, there is a single light transmission window penetrating with the polishing pad, and on the lower surface of the platen, a reflection mirror is attached around the light transmission window and the center of rotation of the platen. A light source and a photodetector are arranged below a reflection mirror attached to the lower surface of the rotation center.

Both of the reflection mirrors are mounted on the lower surface of the platen, so that light emitted from the light source is always transmitted through a half mirror and two reflection mirrors to a single light transmission window regardless of the rotation of the platen. When there is a reflection object on the light transmission window, the light reflected on the light transmission window returns to the same path as described above and enters the photodetector.

That is, while the wafer is being polished, the light detector can take in the reflected light from the polished surface of the wafer while the light transmitting window passes under the wafer for a certain period of time as the platen rotates. . In addition, since the light transmitting window is filled with a light transmitting material, the light passes but the slurry does not leak out of the light transmitting window, so that the leaked slurry contaminates the reflecting surface of the reflecting mirror. Does not occur.

Here, while the light transmission window passes below the wafer with the rotation of the platen, the photodetector can continuously take in the reflected light from the wafer. Needless to say, a plurality of locations may be taken in so as to form several different concentric circles on the wafer.

The amount of light received by the photodetector differs depending on the material of the polished surface of the wafer and the material laminated thereon, and accordingly the output voltage or output current generated by the photodetector differs. That is, the material of the polished surface of the polished wafer can be known continuously from one end of the wafer to multiple ends. Further, since the wafer itself is polished while rotating, it is polished at the same polishing speed on concentric circles having the same peripheral speed during rotation, and the state (material) of the polished surface is different for each concentric circle. May be.

Therefore, a plurality of concentric annular regions divided into the head portion are polished based on the amount of reflection from the one end to the multi-end of the wafer previously received by the photodetector. If the pressurized fluid is supplied at an individual pressure, the object to be polished can be polished flat and in a desired amount.

Next, the planar polishing apparatus of the present invention has the following other optical / control means in addition to the above-mentioned optical / control means. A plurality of optical sensors are arranged below the head section and directly below the platen, and at the same time, they are provided at equal intervals within a range where none of the optical sensors protrude from the wafer, and pass through the center of rotation of the head section. The platen is placed on a line that is translated downward from the concentric circle. In addition, the platen has the same number of optical transmission windows as the optical sensors penetrating with the polishing pad, and all the light transmission windows are located immediately above all the optical sensors. It has a matching positional relationship.

Here, while the plurality of light transmitting windows pass under the wafer with the rotation of the platen, each optical sensor emits the reflected light from the polished surface of the wafer as many times as the number of the light transmitting windows. Receive light. In other words, for each optical sensor,
The reflected light is received a plurality of times from the same concentric circle on the wafer polishing surface. The size of the concentric circle differs depending on the position where the optical sensor is installed. As a result, reflected light is received a plurality of times for each of a plurality of concentric circles on the polished surface of the wafer.

The control unit according to the present invention stores the amount of reflected light received previously and sets the average value for each optical sensor. Can be excluded. That is, the amount of reflected light received from a certain concentric circle on the polished surface of the wafer is the average value of the sum of the amounts of received light excluding abnormal values from reflected light taken in a plurality of times.

As described above, similarly to the first case of the optical / control means using the single light transmission window provided on the platen and the photodetector, the amount of reflected light received by each optical sensor is also reduced this time. On the basis of the above, if a pressurized fluid suitable for the polishing state is supplied at an individual pressure to a plurality of concentric annular regions divided into a head portion, the object to be polished can be polished flat and in a desired amount. Can be.

In addition to these, the control unit of the present invention has the above two optical and control means, and each of them has a single light transmitting window and a plurality of light transmitting windows on the platen. Are arranged in the following positional relationship. A plurality of light transmission windows are attached to the platen upper surface at a position passing through the center of rotation on a line passing through the center of rotation of the platen from the midpoint of the line segment on the concentric circle of the platen placed thereon A single light transmissive window penetrating with the provided polishing pad is arranged. In other words, the single light transmission window and the plurality of light transmission windows on the platen are positioned 180 degrees from the rotation center of the platen.
That is to say, it is located at a position facing each other.

As a result, in principle, during polishing, the above two controls are sequentially performed in accordance with the rotation of the platen, and a plurality of concentric divided parts divided into the head portion twice in total during one rotation of the platen. The pressure of the pressurized fluid can be set for each of these annular regions. Of course, in practice, the pressure setting of the pressurized fluid may be performed periodically instead of every press of the platen.

[0030]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a polishing apparatus according to the present invention. FIG. 1 is a configuration diagram of a planar polishing apparatus showing a basic concept of the present invention, in which a platen 11 penetrating with a polishing pad 13 is provided with a single light transmission window WT and a plurality of light transmission windows Wn, and A part of the platen spindle 12 is shown in a sectional view.

A quartz plate CD is fitted into all the light transmitting windows provided on the platen 11, and a translucent polyurethane rubber plate C is provided on all the light transmitting windows provided on the polishing pad 13.
U is fitted, the upper surface of the polyurethane rubber plate CU is equal to or less than the upper surface of the polishing pad, and the polyurethane rubber plate CU maintains a positional relationship that does not easily hit the wafer polishing surface during polishing.

First, the optical path from the light source 28 to the photodetector 29, which constitutes the first optical means, will be described. On the lower surface of the platen 11, the reflection mirror 26 and the rotation of the platen 11 are arranged around a single light transmission window WT. A reflection mirror 27 is mounted at the center, and a light source 28, a photodetector 29, and a half mirror 30 are fixedly disposed inside the platen main shaft 12 below the reflection mirror 27. If the light emitted from the light source 28 passes through the single light transmission window WT via the half mirror 30 and the two reflection mirrors 26 and 27, and there is a reflective object on the light transmission window, The reflected light returns to the same path described above in reverse, and the light detector 2
9 can be entered. (Note that, in FIG. 1, not only the light path from which the light emitted from the light source 28 passes through the single light transmission window WT but also the reflection object despite the absence of the reflection object on the light transmission window WT can be easily understood. An optical path returning from the light detector 29 to the photodetector 29 is also shown at the same time.)

Regarding the two reflecting mirrors 26 and 27, the light emitted from the light source 28 always returns to the half mirror 30 regardless of the rotation of the platen 11 if there is a reflective object on the light transmitting window WT. The optical path connecting the two reflecting mirrors and the optical path entering the photodetector 29 from the half mirror 30 are provided on the platen main shaft 12 with appropriate light transmitting holes 3.
1 is provided, and the light transmitting hole 31 becomes a part of the optical path.

Next, as a second optical means, a plurality of optical sensors Sn are arranged immediately below the platen 11,
The arrangement is as shown in FIG.
On the concentric circle of the platen 11 passing through the center of rotation of the (wafer), at the same time, they are provided at equal intervals in a range where none of the optical sensors Sn protrude from the wafer. The number of light transmission windows is 5, and S
1 and S5 are located at the peripheral edge of the wafer, S2 and S4 inside each one are located in the middle of the wafer, and S3 is located at the center of the wafer.

The plurality of light transmitting windows Wn provided on the platen 11 are provided on the same concentric circle as the previous optical sensor Sn and are at equal intervals. The transmissive window has a positional relationship that coincides directly above all the optical sensors Sn. The matching state is shown in FIG. 3 (c), and FIGS. 3 (b), (c), (d)
When there are a plurality of light transmitting windows Wn in the state, each optical sensor Sn receives the reflected light from the polished surface of the wafer. Referring back to FIG. 1, the optical sensor Sn has both functions of emitting light and receiving light, and receives light reflected by the polished surface of the wafer by emitting light.

The positional relationship between the single light transmitting window WT used for the first optical means and the plural light transmitting windows Wn used for the second optical means is shown in FIGS. ,
As shown in FIG. 4 (b), the concentric circles on which they are located differ slightly in size. This is platen 1
The reflection mirror 26 attached to the lower surface of the platen 1
This is to avoid colliding with the optical sensor Sn installed below the platen 11 in order to rotate with the rotation of 1, and for example, dispose the optical sensor Sn below to avoid collision between the two. If the optical sensor Sn can receive light, the light transmission windows provided for both optical means can be on the same concentric circle.

Further, the light transmission windows provided for the two optical means are placed on the platen 11 by 180 degrees with respect to the center of rotation of the platen 11 as shown in FIGS. 2 (a), 3 and 4 (b). It is provided in the position where it opposes. Further, an output voltage or an output current generated according to the amount of light received by the light detector 29 and the optical sensor of both optical means is stored and processed by the control unit.

It should be noted that the timing of receiving light with the photodetector 29 and the optical sensor of both optical means is as follows.
A sensor for timing generation may be attached to the platen 11, and an input signal of the sensor may be used as a trigger,
An encoder signal of the platen spindle rotating motor may be used as a trigger. Alternatively, since the reflectivity of the lower surface of the platen 11 is much lower than the reflectivity of the polished surface of the wafer, a threshold is set for the amount of received light while constantly receiving light, and when the threshold is exceeded is triggered. Alternatively, the reflected light from the polished surface of the wafer may be used.

On the other hand, the head section 14 will be described with reference to FIGS. FIG. 5 is a side view showing a partial cross section of the internal structure of the head section 14, and FIG. 6 is a plan view showing a cross section along the AA 'cross section of FIG. The wafer holding surface has a plurality of opening holes 18, 19, 20. The opening holes 18, 19, 20 respectively correspond to a central portion of the wafer,
The middle part and the peripheral part are separately provided at locations corresponding to concentric annular regions. Here, the plurality of opening holes 18 formed in the center portion are formed in the air chamber C for the center portion inside the head portion 14.
A plurality of openings 19 formed in the middle portion are connected to the middle portion air chamber CB1, and a plurality of openings 20 formed in the peripheral portion are formed into the air for the peripheral portion inside the head portion 14. It is connected to room CB2. For the independent air chambers CB0 to CB2, as shown in FIG.
Air having pressures of P0 to P2 is supplied from separate air circuits 0 to 2, respectively.

Therefore, for the wafer 10 to be polished while being sandwiched between the platen 11 and the head portion 14, at the center of the wafer 10, the total of the opening holes 18 provided in F0 (= P0 × CB0) In the middle part of the wafer, the pressing force F1 (= the total cross-sectional area of the opening 19 provided in P1 × CB1), and in the peripheral portion of the wafer 10, F2 (= P2 X (the total cross-sectional area of the opening 20 provided in the CB2). Here, S3 of the optical sensor used for the first optical means extended above is below S0 where the pressing force of F0 is applied.
2 and S4 are below the pressing force of F1 and S
Nos. 1 and S5 are located below where the pressing force F2 is applied.

As shown in FIG. 1, the supplied high-pressure air is supplied to precision regulators R0 and R provided in each air circuit and capable of electrically adjusting the air pressure.
1, and are supplied to the respective air chambers via R2. Also,
The precision regulators R0, R1, and R2 can set their air pressures by the control unit 40. at the same time,
The air pressure can be set based on the output voltage or output current generated according to the amount of light received by the two optical means described above, the light detector 29 and the optical sensor Sn.

The photodetector 29 and the optical sensor Sn
, That is, the amount of reflected light from the polished surface of the wafer depends on the surface material of the polished surface. The reflected light of the main material Cu forming the wiring material layer 3 laminated on the outermost periphery of the wafer has an orange color, and the amount of reflected light therefrom is large. One inner barrier metal layer 2 is mainly made of a material TaN, and its polished surface is gray, and the amount of reflected light is smaller than that of the wiring material layer 3. When the underlying silicon is used, the polished surface generally exhibits a purple color, and the amount of reflected light therefrom is further reduced.
FIG. 8 shows the situation in an image.

As shown in FIG. 5, the head section 14
It is roughly divided into an upper fixed part 16 and a lower rotating part 15. The upper fixed portion 16 is provided with an air inlet 17 around the periphery thereof for supplying air to each of the air chambers, and the lower rotating portion 15 fitted in the cylindrical shape has the air inlet 17 therein. And an air pipe 25 connected to each air chamber. At the same time, although not shown, the lower rotating portion 15 connected to a rotating motor provided above is rotatable without swinging, and the air inlet 1
The cylindrical sliding portion has an O-ring so that the air circuit from 7 to each air chamber is not interrupted during rotary polishing. Also, the upper fixing portion 16
Is configured to be able to move up and down together with the lower rotating portion 15 fitted therein.

The platen 11 having the polishing pad adhered to the upper surface is integrally formed with the platen main shaft 12, and is rotated by rotating the platen main shaft 12 connected to a motor (not shown). It has a structure such as a bearing that enables precision polishing while suppressing runout of the upper surface as much as possible.

[0045]

EXAMPLE 1 Next, referring to FIG. 9, when the wafer is polished flat and fixed amount, the polishing state of the wafer polished surface (in the case where dripping occurs in the peripheral portion of the wafer in a tapered shape as polishing progresses). ) Corresponding to the pressing force F applied from the pad portion to the central portion, the middle portion, and the peripheral portion of the wafer.
A basic setting method of 0 to F2 will be described.

First, in FIG. 9A in the initial state of polishing, polishing is performed while applying a uniform pressing force in a relation of F0 = F1 = F2 to each portion of the wafer. At this time, the photodetector 2
Both 9 and all the optical sensors receive the reflected light of the wiring material layer 3 laminated on the outermost layer of the wafer.

When the polishing is continued, as shown in FIG.
In the peripheral portion, the wiring material layer 3 laminated on the outermost portion of the wafer is removed and the barrier metal layer 2 is exposed on the entire surface, but the wiring material layer is still exposed in the central portion. 3 remains on the entire surface, and the barrier metal layer 2 begins to be exposed in some places in the middle part. At this time, in the first optical means, FIGS. 3A and 4B
In other words, while the single light transmitting window WT passes under the wafer, the reflected light from the polished surface of the wafer is received. As shown in FIG. 4A, the amount of received light is highest at the center where the wiring material layer 3 having a high reflectance remains, and is low at the periphery where the barrier metal layer 2 is exposed. That is, the reflection intensity of the polished surface of the polished wafer can be known continuously from one end of the wafer to multiple ends.

On the other hand, at this time, the second optical means
(B) to (d), as shown in FIG.
While n sequentially passes under the wafer, the reflection amount is measured for each light transmission window by each optical sensor. FIG. 2B shows an image of the measurement result. The sensor 3 is located in the center of the wafer, S2 and S4 are located in the middle of the wafer,
Since 1 and S5 are arranged at the periphery of the wafer, the amount of reflection received by each sensor is the highest at the center and the lowest at the periphery, as obtained by the first optical means. .
In FIG. 2B, three abnormal values are recorded. However, in the control unit 40, for each sensor, the average value of the light reception amount excluding the abnormal value is used as the light reception amount of each sensor.
The amount of received light is as shown in FIG. In other words, it can be seen that the wafer periphery has tapered sag.

Then, as shown in FIG. 9C,
The pressing forces F0, F1, and F2 applied to each part of the wafer are adjusted so that the central part of the wafer is polished more than the peripheral part.
By continuing the polishing while setting so that 0>F1> F2, the peripheral portion of the wafer stops polishing, the wiring material layer 3 in the central portion is polished, and the polishing surfaces of both the peripheral portion and the central portion of the wafer are polished. Then, the wiring material layer 3 and the barrier metal layer 2 are mixed. FIG. 7 illustrates the pressing force applied to each part at this time.

The final finish is, as shown in FIG. 9D, the pressing force F0 applied to the center, middle and peripheral portions of the wafer.
F1 and F2 are returned to the relation of F0 = F1 = F2, and polishing is continued for a certain period of time to completely remove the barrier metal layer 2 remaining on the polished surface of the wafer. Then, the polished surface of the wafer is covered with the wiring material layer 3 for forming the wiring pattern in the underlying silicon 1.
Is left partially. At this time, although not described with reference to the drawings, the polished surface of the wafer generally has a reflection intensity peculiar to the constituent materials described above. Also, in this process, FIG.
At this point, since the polishing surface is flattened and then polished for a certain period of time, if the polishing time is set appropriately, the depth of the wiring pattern in the wafer can be made uniform, and the wiring portion 4 that is easily polished can be formed.
Only the surface sags (dishing, see FIG. 12 (a))
Not even.

As described above, the pressing force F0 when polishing the wafer is
The basic setting method of F2 to F2 has been described. Here, the following is added regarding the timing of changing the pressing forces F0 to F2. As described in Example 1,
While the platen makes one rotation, the constituent material of the polished surface of the wafer is known from the two optical means a total of two times.
Although it is possible to control 0 to F2, it is often the case that a sufficiently flat and desired amount of polishing can be performed without controlling as frequently (for example, 1 second / revolution when the platen rotation speed is 60 rpm). I think. In that case, the following method may be adopted.

While the entire polished surface of the wafer is between the wiring material layers, polishing is continued with the pressing force set to F0 = F1 = F2. Next, even if a part of the polished surface changes to the barrier metal layer, polishing is continued for a certain period of time with the same pressing force F0 = F1 = F2. If the entire polished surface has changed to a barrier metal layer after a certain period of time, the pressing force F0 = F1 = F
Polishing is continued in the state of 2. If after a certain time,
Assuming that the state of the polished surface does not change and the portion which is now the barrier metal layer is the center of the wafer, the pressing force is set to F0 <F1 <F2, and the polishing is further performed for a certain period of time.

Therefore, if the entire polished surface has changed to the barrier metal layer after a certain period of time, the pressing force is set to F0 = F1 = F
The polishing may be continued by returning to step 2. Conversely, if there is no change in the state of the polished surface, the setting of the pressing force remains F0 <F1 <F2 or F0 <<
Polishing is performed under the setting of F1 << F2. This is repeated, and when the entire polished surface of the wafer has changed to the barrier metal layer, the pressing force is returned to F0 = F1 = F2, and polishing is continued.

The predetermined time is not strictly determined, but in the case of polishing a wafer, for example, 5 seconds to 1 second.
About 0 seconds would be reasonable. That is, to the extent permitted,
The wafer can be polished sufficiently flat and a desired amount without changing the pressing force F0, F1, F2 based on the constituent material of the polished surface at regular time intervals, or depending on the case. It is a translation.

Although the polishing method using the planar polishing apparatus of the present invention has been described above, the surface of the platen to which the polishing pad is attached is periodically (for example, once / after polishing one wafer). It is desirable to wash or replace it.
It mainly prevents the slurry from adhering to the polyurethane rubber plate fitted into the polishing pad, which is the optical path of the light emitted from the optical sensor to the wafer polishing surface and the reflected light from the wafer polishing surface. To do that. It is also good to consider that the lower surface of the platen is, for example, a matte black color, the amount of reflected light is kept low, and there is a clear difference from the amount of reflected light from the polished surface of the wafer.

[0056]

Embodiment 2 Next, an example of a planar polishing apparatus using a lower rotating portion 15 having a different structure will be described with reference to FIG. FIG. 10 is a side view of the lower rotating unit 15 shown in a partial cross section. This is a method in which the floating portion 50 not fixed to the outer frame 52 is pressed downward by the airbag 55, and the floating portion 50 is provided with a plurality of air chambers as described in the first embodiment. . The structure and function will be described below.

As an outline, the lower side of the outer frame 52 is hollowed out into a cylindrical shape, and the airbag 55 and the floating portion 50 are sequentially stored therein. A plurality of pins 51 are provided around the floating portion 50, and the outer frame 52 has a fool hole into which the pins 51 are inserted. When the floating portion 50 is fitted into the outer frame 52 as shown in FIG. 10, the floating portion 50 can move slightly in the outer peripheral direction and the vertical direction, and the lower surface thereof can be slightly inclined in an arbitrary direction. is there. Therefore, when the outer frame 52 moves up and down or rotates, the pin 51 is caught in the stupid hole, and the floating portion 50 also moves up and down or rotates. The floating portion 50 is made of a material having high rigidity such as metal or ceramic, and its lower surface is flat, and the wafer 1 is sandwiched between the lower surface and the polishing pad.
0 is polished.

Also, the floating portion 50 reaching the air chamber
The internal air pipe is connected to the air pipe inside the outer frame 52 via the flexible tube 53, and although not shown in detail, P0 to the air chambers CB0 to CB2 are provided.
High-pressure air having a pressure of P2 is supplied. Here, as described above, when the floating portion 50 is fitted into the outer frame 52, the floating portion 50 slightly moves in the outer circumferential direction and the up and down direction, or the lower surface thereof is slightly inclined in an arbitrary direction, as described above. Have enough flexibility.

Next, the original air bag 55 having a cylindrical shape with an open upper surface is provided on the bottom surface of the outer frame 52 which has been hollowed out in a cylindrical shape over the entire periphery of the outer bag 52 with its open end folded back. And a bag mounting plate 57. By tightening the screws 58 at a plurality of locations, the airbag 55 is brought into close contact with the airtight chamber 56. When the high-pressure air PA is supplied, the high-pressure air PA fills the closed chamber 56 without leaking. Thus, the bottom surface of the airbag 55 is in surface contact with the upper surface of the floating portion 50, and constantly applies a constant pressing force over the front surface of the contact surface.

Therefore, in the case of the lower rotating portion 15 of the present configuration, the floating portion 50 rotates while sandwiching the wafer 10 with the lower surface, while easily learning the lower surface of the lower surface easily with the upper surface of the polishing pad. Is possible. Originally, in order to polish the wafer 10 flat, for example, referring to FIG. 1, it is ideal that the lower surface of the head portion 14 (the pressing surface of the wafer 10) and the upper surface of the platen 11 are parallel. However, it is extremely difficult to assemble the apparatus while keeping them parallel, and even if the apparatus is assembled within an allowable range, if the polishing pad 13 slightly undulates during polishing, the lower surface of the head section 14 is removed. It is almost impossible to maintain a parallel relationship with the upper surface of the polishing pad 13. This configuration solves this problem.

Further, in the lower rotating portion 15 shown in FIG. 10, not only the air bag described above but also a plurality of concentric annular regions inside the floating portion 50 as described in detail before the first embodiment. Individual air chambers CB0 to CB2
Are provided, and a floating part 50 is provided from those air chambers.
A plurality of opening holes 18 to 20 penetrate through the lower surface of each. Further, air having pressures of P0 to P2 is supplied to the air chambers CB0 to CB2 from separate air circuits. The air is supplied to each air chamber as an appropriate pressure based on two optical means included in the apparatus and data obtained by the two optical means (not shown), as described in detail before the first embodiment.

That is, in the case of the planar polishing apparatus having the lower rotating portion 15 of the present configuration, the wafer 10 can be polished while the lower surface of the floating portion 50 always follows the upper surface of the polishing pad. , The two controls related to the two optical means are sequentially performed, and a plurality of concentric annular regions divided into the head portion are pressurized for each of the regions twice in total during one rotation of the platen. Since the fluid pressure can be set individually, the wafer 1 having higher flatness
The polishing of 0 can be performed, and the polishing amount can be controlled more precisely.

In the above-described embodiments, three annular regions in which the pressing force can be individually set for the wafer being polished are set to the central portion, the middle portion, and the peripheral portion of the wafer. Optical sensors for each area,
By arranging a high-pressure air precision regulator, it is possible to set the pressing force for each of the subdivided areas.

In addition, the number of optical sensors constituting the second optical means is set to five. However, this is because the polyurethane rubber plate portion fitted into the light transmitting window of the polishing pad does not contribute to polishing. Although there was concern that the capacity would be reduced, if the number of optical sensors was further increased, and at the same time the number of concentric annular regions divided into the head part was also increased, more detailed pressure control could be achieved. Will be possible.

In the embodiment, the pressing force is generated by using high-pressure air. However, the high-pressure fluid used is not limited to high-pressure air, and may be not only high-pressure N2 gas or gas but also high-pressure liquid. By the way, if a high-pressure liquid is selected as the high-pressure fluid to be used, it will be somewhat difficult to provide the following function, but the wafer holding surface in an annular area where the pressing force can be set individually for the wafer being polished. In addition to applying a pressing force to the plurality of opening holes formed in the head, the supply circuit for high-pressure air is switched to a vacuum circuit (not shown) by using a solenoid valve or the like, and conversely, the head becomes a hole for vacuum suction. It is also possible to provide the unit with a function of sucking the wafer and transporting the wafer onto the polishing pad.

In addition, although the present embodiment is a system having only one head unit, a plurality of head units having the same structure can be arranged. In this case, the first head is located below the platen where the head is newly disposed.
It is sufficient to install a plurality of optical sensors, which are optical means, and simply set a new timing for receiving the reflected light, and use the plurality of light transmission windows used in this embodiment as they are. Therefore, it is not necessary to newly provide a light transmission window on the platen.

[0067]

As described above, according to the planar polishing apparatus of the present invention, when polishing an object to be polished on which several kinds of materials are stacked, the platen makes one rotation during polishing using two kinds of optical means. The material left on the polishing surface of the object to be polished can be known alternately twice in each of the plurality of annular regions of the object to be polished, and the polishing pad is polished in each of the plurality of annular regions. Since the force for pressing the object can be set, the polishing can be quickly performed in response to the change in the material of the polished surface, and the polished surface can be polished to a flat surface without being tapered, and a desired amount can be polished. This is more effective when the platen is polished at a low speed.

The above effect becomes more remarkable when the size of the wafer is increased. The polished surface can be polished flat and a desired amount can be polished even for a large wafer. Depth becomes uniform, and it becomes possible to polish an object to be polished with a high quality in which each wiring resistance is constant. Therefore, it will greatly contribute to the improvement of the yield rate for future large wafers.

Further, one of the two types of optical means is to provide a more accurate polished surface in order to make the information on the same portion of the polished surface an average value excluding abnormal values during the multiple times of taking in information. Can be grasped. This also leads to an increase in the yield of large wafers.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a planar polishing apparatus showing a basic concept of the present invention.

FIG. 2A is a plan view of a polishing pad showing the arrangement of a plurality of optical sensors in a partial cross section. (B) An image diagram of the amount of light received from each light transmission window by a plurality of optical sensors.

FIG. 3 is a perspective view illustrating a relationship between a light transmitting window and a wafer polishing position as the polishing pad rotates.

FIG. 4A is a diagram showing the amount of light received by a photodetector while a single light transmission window passes under a wafer. (B) A plan view of the polishing pad when a single light transmission window enters under the wafer.

FIG. 5 is a side view showing the internal structure of the head section of the present invention in a partial cross section.

FIG. 6 is an AA ′ showing the internal structure of the head section of the present invention.
Cross-sectional view along the line.

FIG. 7 is an image diagram showing an average value of the amount of received light obtained under a certain condition of a plurality of optical sensors, and a partial cross-sectional view of a head portion in which a pressing force applied to a sensor arrangement portion is imaged.

FIG. 8 is an image diagram showing a difference in reflectance due to a difference in a material constituting a wafer.

FIG. 9 is a cross-sectional view of a wafer in the process of being polished using the planar polishing apparatus of the present invention.

FIG. 10 is a side view showing a partial cross section of an internal structure of a lower rotating portion of a head portion according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view of a wafer, illustrating a manufacturing process of the wafer.

FIG. 12 is a cross-sectional view of a wafer showing a state of a defective polishing surface.

FIG. 13 is a side view and a sectional view showing a conventional head portion having an annular air chamber therein.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wafer 11 Platen 12 Platen spindle 13 Polishing pad 14 Head part 15 Lower rotating part 16 Upper fixed part 17 Air inlet 18 CB0 opening 19 CB1 opening 20 CB2 opening 25 Air piping 26, 27 Reflection mirror 28 Light source 29 Photodetector 30 Half mirror 31 Light transmission hole 40 Control unit 50 Floating unit 51 Pin 52 Outer frame 53 Flexible tube 55 Airbag 56 Sealed room 57 Bag mounting plate 58 Screw Sn Optical sensor WT Single light transmission window Wn Plural Light transmission window CD Quartz plate CU Polyurethane rubber plate CB0 Air chamber for central part CB1 Air chamber for middle part CB2 Air chamber for peripheral part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Nobuhiro Nagamoto 2-9-1, Hararashi, Otsu-shi, Shiga Nichiden Machine Co., Ltd. (72) Inventor U-ichi Sato 5-7-1 Shiba, Minato-ku, Tokyo No. Within NEC Corporation (72) Inventor Masanari Mitsubashi 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation F-term (reference) 3C034 AA13 AA17 BB93 CA02 CA22 CB04 DD10 3C058 AA07 AA09 AA12 AC02 AC04 BA01 BA02 BA07 BA09 BA14 BB01 BB04 BB09 CB01 DA17

Claims (9)

[Claims] A platen having a polishing pad attached to an upper surface thereof, and a head portion above the platen, wherein a predetermined pressure is applied between the platen and the head portion with a polishing object interposed therebetween. And the head portion is rotated, the polishing object is polished by interposing a slurry between the polishing pad and the polishing object, and a pressure fluid can be ejected to the surface where the head portion holds the polishing object, A plurality of opening holes are provided in a plurality of concentric annular regions divided into the head portion so that a pressurized fluid can be supplied to each of the regions, and the platen penetrates with a polishing pad attached to an upper surface. A single light-transmitting window, a light-transmitting material is fitted into the light-transmitting window, and a reflection mirror is attached to a lower surface of the platen around the single light-transmitting window and a rotation center of the platen. Of the platen In a planar polishing apparatus having a light source and a photodetector below a reflection mirror attached to a lower surface of a center of rotation, light emitted from the light source is transmitted through the two reflection mirrors to the single light transmission unit. The pressure of the pressurized fluid is applied to each region in accordance with the amount of light received by the photodetector that is projected onto the object to be polished through the window, becomes reflected light from the object to be polished, and receives light that returns along the same path as described above. A planar polishing apparatus having a control unit that can be changed. 2. The polishing apparatus according to claim 1, wherein the light detector continuously receives reflected light from the polishing object while the single light transmitting window passes below the polishing object with the rotation of the platen during polishing. 2. The planar polishing apparatus according to claim 1, further comprising a control unit that can change a pressure of the pressurized fluid for each of the areas according to an amount of light received by the photodetector. 3. 3. A platen having a polishing pad attached to an upper surface thereof, and a head portion above the platen, wherein a predetermined pressure is applied between the platen and the head portion with a polishing object interposed therebetween. And the head portion is rotated, the polishing object is polished by interposing a slurry between the polishing pad and the polishing object, and a pressure fluid can be ejected to the surface where the head portion holds the polishing object, In a planar polishing apparatus in which a plurality of opening holes are provided in a plurality of concentric annular regions divided into the head portion and a pressurized fluid can be supplied to each region, the platen is attached to an upper surface. A plurality of light transmitting windows penetrating with the polishing pad, a plurality of light transmitting materials are fitted into the plurality of light transmitting windows, and a plurality of optical sensors are arranged below the platen; Flat polishing equipment characterized by . 4. The optical sensor according to claim 1, wherein the plurality of optical sensors are disposed on a line which is translated downward from a concentric circle of the platen passing through the center of rotation of the head portion, and the plurality of light transmitting windows are arranged on the optical sensor. 4. The planar polishing apparatus according to claim 3, wherein all the light transmission windows have a positional relationship corresponding to a position directly above all the optical sensors. 5. 5. The optical sensor according to claim 1, wherein the plurality of optical sensors are arranged such that the center of the object to be polished is placed at the midpoint of a concentric line segment disposed thereon. The flat-surface polishing apparatus according to claim 4, wherein the flat-surface polishing apparatus is provided at regular intervals in a range that does not protrude from an object. 6. An optical sensor receives light, which is emitted from the optical sensor to the object to be polished and becomes reflected light from the object to be polished, by the optical sensor. The planar polishing apparatus according to claim 5, further comprising a control unit capable of changing each of the pressures. 7. During polishing, the amount of reflected light received from the object to be polished obtained when the plurality of light transmitting windows pass directly above the plurality of optical sensors with the rotation of the platen is determined. The plurality of optical sensors all store and, during the passage of the object to be polished, the number of reflections received by each of the optical sensors equal to the number of the plurality of light transmission windows, the stored reflection. The planar polishing apparatus according to claim 6, wherein an average value of the sum of values obtained by removing abnormal values from the amount of received light is used. 8. The planar polishing apparatus according to claim 5, wherein
In the platen, the plurality of light transmission windows pass through the rotation center on a line passing through the rotation center of the platen from a midpoint of a line segment on a concentric circle of the platen disposed thereon. A single light transmitting window that penetrates with the polishing pad attached to the upper surface of the platen, and a reflection mirror is provided on the lower surface of the platen around the single light transmitting window and the rotation center of the platen. A flat-surface polishing apparatus, wherein a light source and a photodetector are disposed below a reflecting mirror mounted on a lower surface of a rotation center of the platen. 9. The planar polishing apparatus according to claim 8, wherein
The control unit described in claim 6 is provided for the plurality of optical sensors, and the control unit described in claim 2 is provided for the photodetector. Wherein the two controls are sequentially performed, and the pressure of the pressurized fluid can be changed for each of the regions twice in total during one rotation of the platen.