JPH08330398A - Wafer processing method and apparatus - Google Patents

Abstract

PURPOSE: To remove a slurry efficiently without the damaging of the characteristic of a chemical machinery polishing method, by processing the opposite surface of a wafer to a wafer holding surface in the state of the wafer being held using a wafer holding means whereby a fluid is jetted from the whole peripheral edge of the wafer toward its outside. CONSTITUTION: In the state of a wafer 5 being held using a holding means 11 which jets a fluid from the whole peripheral edge of the wafer 5 toward its outside, the opposite surface of the wafer 5 to its holding surface is processed. For example, a carrier 6 holding the wafer 5 is set for the wafer 5 to be opposed to a polishing plate 3. The wafer 5 is held on the carrier 6 by a Bernoulli's chuck 11, and therefore, in the state of the fluid jetting from the periphery of the wafer 5, it is held. In that state, a slurry 2 is fed from a slurry feeding port 1 onto a polishing cloth 9 on the polishing plate 3 to polish the wafer 5 by adjusting the rotary speed of a rotary shaft 4 of the polishing plate 3 and by adjusting the rotary speed of a rotary shaft 7 of the carrier 6 and its pressing pressure 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer processing method and apparatus in a semiconductor device manufacturing process. More specifically, the present invention relates to improvement of a multi-layer wiring forming apparatus and method, for example, reliability in a multi-layer wiring forming process in manufacturing a semiconductor integrated circuit such as a highly miniaturized and highly integrated memory device or logical operation element. The present invention relates to a method of flattening an interlayer insulating film having high properties and a method of forming a metal plug.

[0002]

2. Description of the Related Art As device densities increase, wiring technology is becoming more and more miniaturized and multi-layered, and so-called multi-layer wiring technology in the manufacturing process of semiconductor integrated circuits is becoming more important. is there. However, on the other hand, there is a new problem due to the multilayer structure.

This is because the step of the interlayer insulating film becomes large and steep due to the miniaturization of wiring and the progress of multi-layering, and the processing accuracy and reliability of the wiring formed thereon are lowered. For this reason, it is necessary to improve the flatness of the interlayer insulating film at present when the step coverage of the Al wiring cannot be significantly improved.

Further, the improvement of the flatness of the interlayer insulating film is becoming important from the viewpoint of the reduction of the depth of focus due to the shortening of the wavelength of the lithography, and the improvement of the flatness allows the resolution reaching the limit to be reached. Need to keep.

Various insulating film forming techniques and flattening techniques have been developed so far. However, when applied to a fine and multi-layered wiring layer, insufficient flattening and wiring when the wiring interval is wide The occurrence of so-called "voids" in the interlayer film at the intervals has caused a serious problem such as connection failure between wirings.

Therefore, as a means for improving this problem, recently, a chemical mechanical polishing method (referred to as CMP) conventionally used for mirror polishing of a silicon wafer is applied to planarize the interlayer insulating film as a whole. A global flattening technology that can be used has been studied and partially implemented. This method is regarded as promising as a method that can surely flatten the interlayer insulating film. A brief description of this method is as follows.
A wafer to be polished is fixedly held on a carrier by a vacuum chuck or a mechanical chuck, and the wafer is set so as to face a polishing plate called a platen.
In this state, the slurry is supplied from a polishing particle supply system called a slurry onto the polishing cloth called a pad on the polishing plate via the slurry supply port, and the rotation speed of the polishing plate, the rotation speed of the carrier and the polishing pressure are adjusted. And polish. At this time, KOH or the like is added to etch the insulating film, and the etching is performed in a basic atmosphere. After this chemical mechanical polishing, the slurry or the like is sufficiently removed with a cleaning liquid to complete planarization.

[0007]

However, the above-mentioned conventional CMP method also has some problems to be solved.

One of them is the problem of removing the slurry used for polishing. Chemical mechanical polishing uses abrasive particles called a slurry as described above. After polishing, this slurry needs to be removed from the wafer surface. On the other hand, since a vacuum chuck or a mechanical mechanical chuck is used to hold the wafer on the carrier, the slurry also wraps around the back surface of the wafer during polishing. Therefore, conventionally, the removal of this slurry must be performed on both sides of the wafer, which has been a bottleneck in the chemical mechanical polishing process. The present invention has been made in view of the above problems of the prior art,
An object of the present invention is to provide a wafer processing method and apparatus capable of efficiently removing slurry without impairing the characteristics of the chemical mechanical polishing method.

[0009]

In order to achieve the above object, in the present invention, a holding means for ejecting a fluid from the entire peripheral edge of the wafer to the outside is used to hold the wafer in an opposite direction to the holding surface of the wafer. There is provided a wafer processing method characterized in that a side surface is processed.

In a preferred embodiment, the wafer holding means is a Bernoulli chuck.

In another preferred embodiment, the processing of the wafer is a chemical mechanical polishing process.

In another preferred embodiment, the processing of the wafer is a cleaning processing.

Further, the present invention provides a wafer processing apparatus characterized in that a carrier is fixed to the tip of a rotary shaft, and a Bernoulli chuck for holding a wafer is provided on the carrier.

[0014]

As is well known, the Bernoulli chuck holds an object by ejecting fluid from the back surface of the object to be held to generate a differential pressure. When holding a wafer, a viscous flow of gas is made to flow from the back surface of the wafer, and the wafer is held while allowing the gas to flow from the periphery of the wafer to the outside. Is not in principle.
Therefore, the removal of the slurry is required only on the wafer surface, and the productivity is significantly improved as compared with the conventional method.

Further, although the rough cleaning of the slurry is usually carried out in a chemical mechanical polishing apparatus, the rough cleaning of the slurry is carried out, for example, by spin cleaning while holding the wafer on the Bernoulli chuck. Can be done.

[0016]

EXAMPLES Specific examples of the present invention will be described below.

Prior to the description of the actual polishing process, the chemical mechanical polishing apparatus used to carry out the present invention will be described with reference to FIG. FIG. 1 shows an outline of this polishing apparatus. The carrier 6 holding the wafer 5 is set so that the wafer 5 faces the polishing plate 3 called a platen. The wafer 5 is held on the carrier 6 by the Bernoulli chuck 11. Therefore, the wafer 5 is held in a state where the fluid is ejected from the periphery of the wafer 5. In this state, the slurry 2 stored in the slurry supply system 10 is fed from the slurry supply port 1 to the polishing cloth 9 called a pad on the polishing plate 3.
Then, the rotation number of the polishing plate rotating shaft 4, the rotation number of the rotating shaft 7 of the carrier 6, and the pressing pressure 8 of the polishing pressure adjuster (not shown) are adjusted to perform polishing.

There are no particular restrictions on the wafer mounting method, the platen, the number and structure of carriers, and the types of pads and slurries.

FIG. 2 is a structural explanatory view showing the holding principle of the Bernoulli chuck 11. The wafer 5 is held by the Bernoulli chuck 11 while flowing out gas from the surroundings by jetting a viscous flow of gas from the back surface side. In this state, the surface (lower surface) opposite to the holding surface (upper surface in the figure) of the wafer 5
Is polished by a polishing plate. Therefore, the slurry does not flow into the back surface side of the wafer 5 during polishing. After polishing, the wafer is conveyed to the cleaning unit while chucked, and as shown in the figure, the chemical solution (cleaning solution) is jetted from the chemical solution supply port 13 of the chemical solution nozzle 12 to the lower surface of the wafer 5 to clean and remove the slurry. In this case, since the slurry does not adhere to the back surface (upper surface) of the wafer, only the lower surface needs to be cleaned.

(Embodiment 1) In this embodiment, an insulating film between Al wiring layers is flattened by using the above CMP apparatus. As shown in FIG. 3A, a first interlayer insulating film 102 made of silicon oxide and an Al wiring layer 103 are formed on a semiconductor substrate 101 made of silicon, and a second interlayer film 104 is further formed. Prepared wafers. All this was done in the usual way.

Next, chemical mechanical polishing of the second interlayer film 104 was performed using the polishing apparatus shown in FIG. 1 under the following conditions. The Bernoulli chuck shown in FIG. 3 was used as the wafer holding means. Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min These polishing conditions are general polishing conditions for insulating films. Here, a slurry prepared by suspending the slurry in KOH / water / alcohol was used because polishing is performed in a basic atmosphere.

As a result, in the conventional chemical mechanical polishing apparatus, the slurry that has also spilled over to the back surface of the wafer is suppressed in the present invention, and the slurries are suppressed, resulting in uniform planarization as shown in FIG. 3B. I was able to process it. After that, although not shown, the slurry is roughly removed by a washing machine generally incorporated in the chemical mechanical polishing apparatus.

Next, the substrate is conveyed to the cleaning apparatus of the present invention in a wet state so that the residual slurry does not adhere to the substrate, and the residual slurry on the substrate surface is spun while the substrate is held on the Bernoulli chuck shown in FIG. It was removed by washing. The chemicals used were SC-1 and dilute hydrofluoric acid in this order, and finally rinsed with pure water. By doing so, the slurry removed from the front surface of the substrate did not spill around to the back surface of the substrate, and the slurry could be removed to a practical level.

(Embodiment 2) In this embodiment, the metal film of the blanket W at the time of forming the Al wiring layer is averaged. As shown in FIG. 4A, a first interlayer insulating film 102 made of silicon oxide and an Al wiring layer 103 are formed on a semiconductor substrate 101 made of silicon, and a second interlayer film 104 is further formed. After forming the opening 105, a blanket tungsten 106 was prepared to be embedded in the opening 105 to prepare a wafer. All this was done in the usual way.

Next, chemical mechanical polishing was performed using the polishing apparatus shown in FIG. 1 under the following conditions. The Bernoulli chuck shown in FIG. 2 was used as the wafer holding means.

Polishing plate rotation speed: 50 rpm Carrier rotation speed: 17 rpm Polishing pressure: 10 psi Polishing pad temperature: 30 to 40 ° C. Slurry flow rate: 225 ml / min These polishing conditions are common as film polishing conditions. Here, a slurry prepared by suspending the slurry in diluted hydrofluoric acid / water / alcohol was used because polishing is performed in an acidic atmosphere.

As a result, in the conventional chemical mechanical polishing apparatus, the slurry that has also spilled over to the back surface of the wafer is suppressed in the present invention, and the slurry phenomenon is suppressed. I was able to. After that, although not shown, the slurry is roughly removed by a washing machine generally incorporated in the chemical mechanical polishing apparatus.

Next, the substrate is transferred to the cleaning apparatus of the present invention in a wet state so that the residual slurry does not stick to the substrate, and the residual slurry on the substrate surface is spun while the substrate is held on the Bernoulli chuck shown in FIG. It was removed by washing. The chemicals used were SC-1 and dilute hydrofluoric acid in this order, and finally rinsed with pure water. By doing so, the slurry removed from the front surface of the substrate did not spill around to the back surface of the substrate, and the slurry could be removed to a practical level.

(Embodiment 3) In this embodiment, the interlayer insulating film is planarized by chemical mechanical polishing through the same process as in Embodiment 1, and then the wafer is polished while being held on the same Bernoulli chuck. The carrier was carried away from the plate, carried to another portion (cleaning section) of a chemical mechanical polishing apparatus (not shown), and a chemical solution was sprayed onto the wafer surface as shown in FIG. 2 to remove the surface slurry. In this case, since the Bernoulli chuck is used, the slurry on the front surface of the wafer does not get around to the back surface of the wafer during cleaning.
Therefore, only the surface needs to be cleaned. If you do this,
The apparatus can be made compact and the productivity of removing the slurry can be improved. Here, the point is to remove the slurry while holding it on the same Bernoulli chuck, and various forms can be considered.

The present invention is not of course limited to the three embodiments described above, and the structure, conditions, etc. can be appropriately changed without departing from the gist of the present invention.

The Bernoulli chuck may be used in combination with another mechanical chuck to hold the wafer.

Further, the wafer is not limited to the Bernoulli chuck, and the wafer may be held by combining a means for ejecting a fluid from the back side of the wafer and a mechanical holding means.

[0033]

As described above, according to the present invention,
Since impurities such as slurry do not get around to the back side of the wafer while holding the wafer, the wafer can be processed on only one side, and the slurry can be removed and cleaned easily and chemically. It becomes possible to flatten by mechanical polishing.

Therefore, the VLSI can be manufactured with high productivity in a highly reliable process.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a chemical mechanical polishing processing apparatus according to an embodiment of the present invention.

FIG. 2 is a principle explanatory view showing a holding action of the Bernoulli chuck according to the embodiment of the present invention.

FIG. 3 is an explanatory view showing a first example of a polishing process by the chemical mechanical polishing processing apparatus according to the embodiment of the present invention.

FIG. 4 is an explanatory view showing a second example of the polishing process by the chemical mechanical polishing processing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1: Slurry supply port, 2: Slurry, 3: Polishing plate, 4: Rotation axis, 5: Wafer, 6: Carrier, 7: Rotation axis, 8: Pressing pressure, 9: Polishing cloth, 10: Slurry supply system, 11 : Bernoulli chuck.

Claims (5)

[Claims] 1. A wafer processing method, characterized in that a surface opposite to a holding surface of the wafer is processed while the wafer is held by using a holding means for ejecting a fluid from the entire peripheral edge of the wafer to the outside. 2. The wafer processing method according to claim 1, wherein the wafer holding means is a Bernoulli chuck. 3. The wafer processing method according to claim 1, wherein the processing of the wafer is a chemical mechanical polishing processing. 4. The wafer processing method according to claim 1, wherein the processing of the wafer is a cleaning processing. 5. A wafer processing apparatus, wherein a carrier is fixed to the tip of a rotating shaft, and a Bernoulli chuck for holding a wafer is provided on the carrier.