JPH10242090A - Method of polishing semiconductor wafer and polishing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply eliminate dust residue on a wafer surface, by adequately using chemicals in the course of a series of sequence from wafer surface polishing to in-line cleaning in a CMP(chemical mechanical polishing) process. SOLUTION: When this method is used and the polishing of an element formation surface of a semiconductor wafer which is used in a CMP process in the course of semiconductor device manufacture is performed, abrasive liquid, chemicals, and mixed solution of them are sequentially supplied from a slurry supplying port 112 to a polishing pad for wafer polishing, and polishing is performed. In this process, supply and interruption of the abrasive liquid, the chemicals and the mixed solution of them are controlled. Thereby the form of the element forming surface after polishing is controlled, and flaw and dust of the element forming surface are restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing
The present invention relates to a polishing method and a polishing apparatus used in a shing (CMP) process, and particularly to a method and an apparatus for supplying a polishing liquid onto a polishing pad.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, flattening after depositing an interlayer insulating film in a multilayer wiring process, flattening a metal film buried in a hole opened in the interlayer insulating film, and flattening an insulating film buried in a trench. To do CMP
Processes are being adopted.

FIG. 4 schematically shows an example of a conventional CMP apparatus used in a CMP process. In FIG. 4, a polishing cloth (polishing pad) 53 is mounted on a polishing plate (surface plate) 52 driven to rotate by a polishing plate rotating shaft 51. A carrier 54 on which a wafer 50 is set so as to face the polishing pad 53 is attached to a carrier rotating shaft 55. Then, a polishing liquid (slurry) 57 containing an abrasive (including abrasive particles) is supplied from a slurry supply nozzle 56 onto the polishing pad 53, and the polishing pressure is adjusted by a polishing pressure regulator 58.

The most problematic point in the above-described CMP process is that abrasive particles and the like remain on the element formation surface as dust after the element formation surface is polished. Conventionally, as a wafer cleaning method for removing dust on the element formation surface after the above-described CMP, there is a method of controlling abrasive particles and zeta potential of the wafer surface. For example, it is a method of supplying a surfactant to the polishing pad after polishing the element formation surface, or supplying a surfactant to the in-line cleaning unit when cleaning the element formation surface.

However, in the conventional wafer cleaning method, since a plurality of slurries are supplied to the polishing pad or the in-line cleaning unit, the structure of the slurry supply pipe is complicated, and the plurality of slurries are blended at a processing point. In this case, it is difficult to mix uniformly.

Further, when a liquid which is apt to be degraded by volatility or oxidation is used as a solvent for the surfactant, the purpose of the surfactant during the progress of the process is affected by air mixing from the tip of the surfactant supply nozzle. It is difficult to obtain the performance to perform.

On the other hand, from a manufacturing point of view, an apparatus having a complicated piping structure such as the above-mentioned slurry supply pipe is not only expensive but also has a high failure rate, and further requires replacement of the polishing pad. Will lead to worse maintenance.

Japanese Patent Application Laid-Open No. 2-181924 discloses a technique of removing a surface oxide film with an aqueous solution containing silica particles and then polishing the silicon surface with an aqueous amine solution. Also, JP-A-4-129664 discloses that
There is disclosed a technique in which a polishing liquid having large abrasive particles, pure water, and a polishing liquid having small abrasive particles are sequentially switched during polishing of the element formation surface. Japanese Patent Application Laid-Open No. 7-221067 discloses that C
A technique is disclosed in which the viscosity of a slurry solution is adjusted and supplied by a mixer during MP. Also, Japanese Patent Application Laid-Open No.
No. 9060 discloses a technique for flattening a buried connection hole by successively switching in the order of a polishing liquid for a metal film, pure water, and a polishing liquid for an insulating film.

However, in each of the above-mentioned known examples, there is disclosed a technique for preventing abrasive particles and the like from remaining as dust on the element forming surface after the element forming surface is polished by using a chemical solution by an appropriate method during the element forming surface polishing. Not disclosed.

[0010]

As described above, the conventional method of polishing a semiconductor wafer removes abrasive particles and the like as dust on the element formation surface after polishing the element formation surface in the CMP process after polishing the element formation surface, There were various problems associated with this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an element forming surface is formed by using a chemical solution by an appropriate method during a series of sequences from polishing of an element forming surface to in-line cleaning in a CMP process. It is an object of the present invention to provide a semiconductor wafer polishing method and a polishing apparatus which can easily remove the dust residue.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method of polishing a semiconductor wafer used in a CMP process in a semiconductor device manufacturing process, wherein at least a part of the polishing method is performed on a polishing pad facing an element forming surface of the semiconductor wafer. During the polishing process by sequentially supplying a polishing liquid containing a polishing agent, a chemical liquid, and a mixed liquid thereof from one slurry supply port, and controlling the supply / stop of the polishing liquid, the chemical liquid, and a mixed liquid thereof by controlling It is characterized in that the shape of the element formation surface after polishing is controlled and scratches and dust on the element formation surface are suppressed.

[0013] A polishing apparatus for polishing a semiconductor wafer according to the present invention comprises: a polishing pad for polishing an element formation surface of a semiconductor wafer;
A mixing tank through which a polishing liquid for polishing the element-forming surface and a chemical liquid for cleaning the element-forming surface can pass or be mixed; and a plurality of types of polishing liquids and at least one chemical liquid corresponding to the mixing tank are respectively predetermined. A supply pipe with a valve for supplying at the timing of
A control device for controlling a valve of the supply pipe with a valve so as to continuously supply the polishing liquid or the chemical liquid or a mixture thereof from the mixing tank to the two slurry supply ports in a predetermined sequence. It is characterized by.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 schematically shows the configuration of a system using a semiconductor wafer polishing apparatus according to a first embodiment of the present invention. In the following description, the term abrasive includes abrasive particles.

1 is a polishing zone, 2 is a wafer cleaning zone, and 3 is a wafer transfer zone. In the polishing zone 1, reference numeral 11 denotes a slurry supply nozzle / mixing unit, and reference numeral 12 denotes a polishing section. In the wafer cleaning zone 2, reference numeral 21 denotes a wafer delivery station;
Reference numeral 22 denotes an in-line cleaning unit having a brush station 221 and a rinsing / spin drying station 222. In the wafer transfer zone 3, 31
Denotes a wafer transfer station, and 32 denotes a wafer transfer station.

FIG. 2 schematically shows the structure of the polishing zone 1 in FIG. 1 taken out. In the polishing section 12, 1
Reference numeral 21 denotes a polishing plate (turntable), which is connected to a rotating shaft 122 so as to be rotatable.
Is attached. A carrier 124 on which the semiconductor wafer 10 is set is provided attached to a carrier rotating shaft 125 so as to face at least a part of the upper surface of the polishing pad 123. Typically, the carrier 124
A plurality of sets of carrier rotating shafts 125 are provided, each of which is rotatable in opposition to the polishing pad 123 with a semiconductor wafer set. Note that 12
5 is a polishing pressure regulator.

In the slurry supply nozzle / mixing unit 11, reference numeral 111 denotes a mixing tank capable of passing or mixing a polishing liquid for polishing an element forming surface of a semiconductor wafer, a chemical solution for cleaning an element forming surface, and pure water for cleaning a polishing pad. It is. 11
Reference numeral 2 denotes a slurry supply port for supplying a polishing liquid 113, a chemical liquid, a mixed liquid, or pure water onto the polishing pad 123, and includes, for example, a nozzle connected to the mixing tank.

A plurality of polishing liquid supply pipes with valves and a plurality of chemical liquid supply pipes with valves are connected to the mixing tank 111 for supplying a plurality of types of polishing liquids and a plurality of types of chemical liquids at predetermined timings.

In the present embodiment, a first supply pipe 131 for supplying a first polishing liquid and a second supply pipe for supplying a second polishing liquid are used as the plurality of polishing liquid supply pipes with valves. 132, a first valve 141 and a second valve 142 attached to the supply pipes 131 and 132, respectively. In addition, as the chemical liquid supply pipes with a plurality of valves, a first chemical liquid supply pipe 151 for supplying a first chemical liquid, a second chemical liquid supply pipe 152 for supplying a second chemical liquid, Tubes 151, 152
3rd valves 1 respectively installed corresponding to
43 and a fourth valve 144 are provided.

Further, a pure water supply pipe with a valve in which a fifth valve 145 is added to the pure water supply pipe 16 for supplying ultrapure water (DIW) is connected to the mixing tank 111.

The first valve 141 to the fifth valve 145 are controlled so that the polishing liquid, the chemical liquid, the mixed liquid, and the ultrapure water are continuously supplied to the slurry supply nozzle 112 in a predetermined sequence. Control device 17 is provided.

Next, as a first embodiment of the method for polishing a semiconductor wafer of the present invention, which is carried out using the polishing apparatus of FIG. 2, for example, as shown in FIG.
Oxide film (for example, silicon oxide film) 41 formed on top
A sequence for polishing the film to be polished (polycrystalline silicon film 42 in this example) embedded in the groove (trench) using the oxide film as a stopper film will be described.

(1) First, in order to remove the natural oxide film 43 on the polycrystalline silicon film 42 shown in FIG. 3A, a first polishing liquid having a high polishing rate for the silicon oxide film 41 is applied to the first polishing liquid. The natural oxide film 43 is removed by controlling the valve 141 and supplying the slurry from the slurry supply nozzle 112 onto the polishing pad 123 through the mixing tank 111 as shown in FIG. 3B.

(2) After removing the natural oxide film 43,
The supply of the first polishing liquid is stopped by controlling the first valve 141, and the polishing speed for the polycrystalline silicon film 42 is higher than the polishing speed for the silicon oxide film 41.
Is selected by controlling the second valve 142, and supplied from the slurry supply nozzle 112 to the polishing pad 123 through the mixing tank 111 by using the polishing liquid (for example, using an organic amine-based colloidal silica as a polishing agent). Then, the polycrystalline silicon film 42 is polished.

(3) The polishing of the polycrystalline silicon film 42 proceeds, and immediately before the silicon oxide film 41 as the stopper film is exposed as shown in FIG. By selecting a first chemical (a surfactant or a cellulose or a polysaccharide), the first chemical is mixed with the second polishing liquid in the mixing tank 111 and supplied onto the polishing pad 123 from the slurry supply nozzle 112.

At this time, the polishing pad 123 is hardened at the same time as the viscosity of the slurry increases, so that the polishing rate decreases, but dishing in the trench portion can be suppressed.

(4) When the polishing of the polycrystalline silicon film further proceeds and the silicon oxide film 41 as the stopper film is exposed as shown in FIG. The supply of the second polishing liquid is stopped, and the supply of only the first chemical liquid is continued.

When a polysaccharide such as cellulose or pullulan is used as the first chemical solution, triethanolamine is effective as a solvent for dissolving the polysaccharide, and triethanolamine is controlled by controlling the fourth valve 144. Ethanolamine is selected and supplied into the mixing tank 111.
The above triethanolamine has a function of potential control,
In particular, a silicon oxide film 41 may be used as a part of the stopper film.
At the same time, if the silicon nitride film is exposed,
This has the effect of preventing dust adsorption on the silicon nitride film.

After the element formation surface is polished, a fine scratch called microscratch may remain on the element formation surface. In order to remove the damage, the first chemical solution in the process (3) is used. In the initial stage of mixing with the second polishing liquid, finer polishing particles than those in the second polishing liquid are selected and supplied into the mixing tank 111, and the first chemical liquid is added to the first polishing liquid. The mixture may be supplied from the slurry supply nozzle 112 onto the polishing pad 123.

(5) After polishing of the element formation surface is completed,
The supply of the first chemical solution is stopped by the control of the third valve 143, ultrapure water is selected by the control of the fifth valve 145, and the slurry is supplied from the slurry supply nozzle 112 to the polishing pad 123 through the mixing tank 111. By supplying pure water alone, the residue on the polishing pad 123 is removed.

The same sequence can be applied to polishing a film to be polished buried in a hole (for example, a contact hole) formed in the silicon oxide film 41 using the oxide film as a stopper film.

When the object to be polished is an insulator, it is desirable to use the second polishing liquid prepared to be alkaline by using an organic alkali solution or an inorganic alkali solution as a solvent for the polishing agent. In this case, the solvent of the second polishing liquid desirably contains any of polysaccharides such as cellulose and a water-soluble polymer. In the present embodiment, the polishing agent in the second polishing liquid is preferably an organic solvent. Amine-based colloidal silica is used.

On the other hand, when the metal film is buried as the film to be polished and then the metal film is polished using the silicon oxide film as a stopper film, the second polishing liquid is made acidic as a solvent of the polishing agent. It is desirable to use those prepared.

[0034]

As described above, according to the present invention, CMP
A semiconductor wafer polishing method and apparatus capable of easily removing dust residue on a wafer surface by using a chemical solution in an appropriate manner during a series of processes from wafer surface polishing to in-line cleaning in a process. it can.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view schematically showing a system that uses a semiconductor wafer polishing apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing an example of a configuration by taking out a polishing zone in FIG. 1;

FIG. 3 is a cross-sectional view showing an example of a process in which a semiconductor wafer to be polished is polished in the first embodiment of the semiconductor wafer polishing method of the present invention.

FIG. 4 is a configuration explanatory view schematically showing an example of a conventional CMP apparatus used in a CMP process.

[Explanation of symbols]

 11: slurry supply nozzle / mixing unit, 111: mixing tank, 112: slurry supply nozzle, 113: polishing liquid, 12: polishing section, 121: polishing table, 123: polishing pad, 131, 132: polishing liquid supply pipe, 141 -145 ... first valve-fifth valve, 151, 152 ... chemical supply pipe, 16 ... pure water supply pipe, 17 ... control device.

Claims (10)

[Claims] 1. A method of polishing a semiconductor wafer used in a chemical mechanical polishing process in a semiconductor device manufacturing process, comprising:
A polishing liquid containing a polishing agent, a chemical liquid, and a mixture of these liquids are sequentially supplied from one slurry supply port to a polishing pad at least partially facing the element forming surface of the semiconductor wafer. Polishing a semiconductor wafer by controlling the supply and stop of a polishing liquid, a chemical solution, and a mixture thereof to control the shape of the element forming surface after polishing and to suppress scratches and dust on the element forming surface. Method. 2. The method for polishing a semiconductor wafer according to claim 1, wherein a film to be polished embedded in a groove or a hole formed in an oxide film or a silicon nitride film on the semiconductor wafer is formed on the oxide film or the silicon. When polishing using a nitride film as a stopper film, (1) removing a natural oxide film on the film to be polished by supplying a first polishing liquid having a high polishing rate for the oxide film; After removing the natural oxide film, the supply of the first polishing liquid is stopped, and a second polishing liquid having a polishing rate for the film to be polished higher than that for the oxide film is supplied. Polishing the film to be polished; and (3) mixing the first chemical solution with the second polishing agent immediately before the polishing of the film to be polished proceeds and exposing the oxide film. (4) stopping the supply of the second polishing liquid when the oxide film is exposed, and continuing to supply only the first chemical liquid, and (5) an element formation surface of the semiconductor wafer. Removing the residue on the polishing pad by supplying only pure water to the polishing pad after the polishing is completed. 3. The method of polishing a semiconductor wafer according to claim 2, wherein in the step (3), the first chemical liquid is mixed with the second abrasive in the second polishing liquid at an initial stage. A polishing method for polishing a semiconductor wafer, wherein fine scratches are left on the element formation surface by mixing finer polishing particles than the above polishing particles. 4. The method for polishing a semiconductor wafer according to claim 2, wherein the film to be polished is an insulating film, and the second polishing liquid is an organic alkali solution or an inorganic alkali solution as a solvent for a polishing agent. A method for polishing a semiconductor wafer, which is used. 5. The method for polishing a semiconductor wafer according to claim 2, wherein the film to be polished is a metal film, and the second polishing liquid uses an acidic solution as a solvent for a polishing agent. Semiconductor wafer polishing method. 6. The method for polishing a semiconductor wafer according to claim 4, wherein the solvent contains any of cellulose, polysaccharide, and a water-soluble polymer. 7. The method for polishing a semiconductor wafer according to claim 4, wherein an organic amine-based colloidal silica is used as a polishing agent in the second polishing liquid. 8. The method for polishing a semiconductor wafer according to claim 1, wherein a surfactant, cellulose, or a polysaccharide is used as the first chemical solution. Polishing method. 9. The method for polishing a semiconductor wafer according to claim 8, wherein when a silicon nitride film is exposed simultaneously with a silicon oxide film as a part of said stopper film, said silicon nitride film is dissolved to dissolve said cellulose or polysaccharide. A method for polishing a semiconductor wafer, wherein triethanolamine is used as a solvent. 10. A polishing pad for polishing an element forming surface of a semiconductor wafer, a mixing tank through which a polishing liquid for polishing the element forming surface and a chemical solution for cleaning the element forming surface can be passed or mixed, A plurality of polishing liquids and at least one
A supply pipe with a valve for supplying each type of chemical liquid at a predetermined timing, and the polishing liquid or the chemical liquid or a mixture thereof from the mixing tank to one slurry supply port on the polishing pad. A control device for controlling a valve of the supply pipe with a valve so as to continuously supply the semiconductor wafer in the sequence of (1).