SEMICONDUCTOR DEVICE MANUFACTURING METHOD AND CHEMICAL MECHANICAL POLISHING METHOD

Abstract

According to one embodiment, a semiconductor device manufacturing method comprises forming a film to be polished on a semiconductor substrate, and performing a CMP method on the film to be polished. The CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-132383, filed Jun. 11, 2012, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor device manufacturing method and chemical mechanical polishing method.

BACKGROUND

Semiconductor device manufacturing steps include shallow trench isolation (STI)-chemical mechanical polishing (CMP) and pre-metal dielectric (PMD)-CMP. In these CMP methods, a film to be polished such as a silicon oxide film formed on a semiconductor substrate is planarized.

For example, a ceria-based slurry is used in the planarization (CMP) of a silicon oxide film. The ceria-based slurry has a high polishing rate for a silicon oxide film, and has a high planarization performance. Even when using the ceria-based slurry, however, many scratches are produced on the surface of a film to be polished (silicon oxide film) after CMP, depending on the surface state of a polishing pad. As a consequence, the yield and reliability decrease.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the arrangement of a CMP apparatus according to an embodiment;

FIG. 2 is a plan view showing the CMP apparatus according to the embodiment;

FIG. 3 is a flowchart showing a semiconductor device manufacturing method according to the embodiment;

FIG. 4 is a view for explaining the Rsk value;

FIG. 5 is a graph showing the relationship between the Rsk value on the surface of a polishing pad and the number of scratches on the surface of a film to be polished in a polishing experiment;

FIG. 6 is a graph showing the relationship between the surface temperature and Rsk value of a polishing pad in a conditioning experiment; and

FIGS. 7 and 8 are sectional views showing semiconductor device STI manufacturing steps according to the embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor device manufacturing method comprises forming a film to be polished on a semiconductor substrate, and performing a CMP method on the film to be polished. The CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

This embodiment will be explained below with reference to the accompanying drawings. In these drawings, the same reference numbers denote the same parts. Also, a repetitive explanation will be made as needed.

Embodiment

The embodiment will be explained with reference to FIGS. 1, 2, 3, 4, 5, 6, 7, and 8. In this embodiment, in a CMP method of a semiconductor device manufacturing method, the surface of a polishing pad 11 is conditioned such that the Rsk value becomes negative, and a film to be polished is brought into contact with (slid against) the rotating polishing pad 11. This can reduce scratches on the surface of the film to be polished after CMP. The semiconductor device manufacturing method according to the embodiment will be explained in detail below.

[CMP Apparatus]

First, a CMP apparatus according to this embodiment will be explained below with reference to FIGS. 1 and 2.

FIG. 1 is a view showing the arrangement of the CMP apparatus according to the embodiment. FIG. 2 is a plan view showing the CMP apparatus according to the embodiment.

As shown in FIG. 1, the CMP apparatus according to this embodiment includes a turntable 10, polishing pad 11, top ring 12, slurry supply nozzle 13, dressing liquid supply nozzle 14, dresser 15, and inlet temperature measurement device 16.

The top ring 12 holding a semiconductor substrate 20 is brought into contact with the polishing pad 11 attached to the turntable 10. A film to be processed such as a silicon oxide film is formed on the semiconductor substrate 20. The turntable 10 can rotate at 1 to 200 rpm, and the top ring 12 can also rotate at 1 to 200 rpm. The turntable 10 and top ring 12 rotate in the same direction, for example, counterclockwise. Also, the turntable 10 and top ring 12 rotate in a predetermined direction during CMP. The polishing load of these members is normally about 50 to 500 hPa.

The slurry supply nozzle 13 is positioned above the polishing pad 11. The slurry supply nozzle 13 can supply a predetermined liquid chemical as a slurry at a flow rate of 50 to 1,000 cc/min. Note that the slurry supply nozzle 13 is positioned near the center of the turntable 10, but the position is not limited to this, and the slurry supply nozzle 13 may also appropriately be positioned so as to supply the slurry on the entire surface of the polishing pad 11.

The dresser 15 conditions the surface of the polishing pad 11 when brought into contact with the polishing pad 11. The dresser 15 can rotate at 1 to 200 rpm. The dresser 15 rotates, for example, counterclockwise. Also, the turntable 10 and dresser 15 rotate in a predetermined direction during conditioning. The dressing load of the dresser 15 is normally about 50 to 500 hPa. The inlet temperature measurement device 16 as an infrared radiation thermometer is attached to a pillar portion (dresser driving shaft) connected to the dresser 15. Details of the inlet temperature measurement device 16 will be described later.

In addition, the dressing liquid supply nozzle 14 is positioned above the polishing pad 11. The dressing liquid supply nozzle 14 can supply a predetermined liquid as a dressing liquid at a flow rate of 50 to 1,000 cc/min. Note that the dressing liquid supply nozzle 14 is positioned near the center of the turntable 10, but the position is not limited to this, and the dressing liquid supply nozzle 14 may also appropriately be positioned so as to supply the dressing liquid on the entire surface of the polishing pad 11.

The dressing liquid is, for example, pure water, and the supply temperature of the liquid is appropriately set. By controlling this dressing liquid supply temperature, the inlet temperature to be measured by the inlet temperature measurement device 16 can be adjusted.

As shown in FIG. 2, the inlet temperature measurement device 16 is installed upstream in the rotating direction of the turntable 10 with respect to the dresser 15. Therefore, the inlet temperature measurement device 16 measures the surface temperature (inlet temperature) of the polishing pad 11 on the upstream side in the rotating direction of the turntable 10 with respect to the dresser 15.

The inlet temperature measurement device 16 measures the temperature of the polishing pad 11 on a circular orbit X passing a center O′ of the dresser 15 and having a predetermined distance from a center O of the turntable 10. This is so because the time during which the dresser 15 and polishing pad 11 are in contact with each other is long on the circular orbit X, and so the highest temperature can be measured.

Near the edge of the dresser 15, the dressing liquid collides against the dresser 15 and rises. When temperature measurement is performed near the edge of the dresser 15, therefore, the inlet temperature measurement device 16 may measure not the surface temperature of the polishing pad 11 but the temperature of the dressing liquid by mistake. To measure the surface temperature of the polishing pad 11, the inlet temperature measurement device 16 desirably measures the temperature at an inlet temperature measurement point A positioned on the circular orbit X and spaced apart by a distance d (for example, 10 mm) from the dresser 15.

Note that when the dressing liquid is supplied to the entire surface of the polishing pad 11, it is possible to measure the temperature at any point on the surface of the polishing pad 11, including the inlet temperature measurement point A, as the surface temperature of the polishing pad 11. That is, the inlet temperature measurement device 16 can be installed in any position as long as the temperature at any point on the surface of the polishing pad 11 can be measured.

[Manufacturing Method]

Next, the semiconductor device manufacturing method according to this embodiment will be explained with reference to FIG. 3.

FIG. 3 is a flowchart showing the semiconductor device manufacturing method according to the embodiment.

As shown in FIG. 3, in step S1, a film to be polished is formed on the semiconductor substrate 20. This film to be polished is, for example, a silicon oxide film when forming an STI structure or PMD structure, but is not limited to this.

Then, in step S2, a CMP method is performed on the film to be polished. In this step, the CMP method according to this embodiment is performed under the following conditions.

First, in step S21, the polishing pad 11 is conditioned. More specifically, the dresser 15 is brought into contact with the surface of the polishing pad 11, and slid against the polishing pad 11. In addition, the dressing liquid supply nozzle 14 supplies the dressing liquid, for example, pure water to the surface of the polishing pad 11.

As the polishing pad 11, a material mainly containing polyurethane and having a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa is attached to the turntable 10. Also, the rate of rotation of the turntable 10 is set at, for example, 10 (inclusive) to 110 (inclusive) rpm. As the dresser 15, a material having a diamond roughness of #100 (inclusive) to #200 (inclusive) (manufactured by Asahi Diamond) is used. The rate of rotation of the dresser 15 is set at 10 (inclusive) to 110 (inclusive) rpm, and the dressing load is set at 50 (inclusive) to 300 (inclusive) hPa. The conditioning time is set at 60 s.

When supplying pure water, the supply temperature and supply flow rate of the pure water are controlled so that the surface temperature of the polishing pad 11 (the temperature measured at the inlet temperature measurement point A by the inlet temperature measurement device 16) is 23° C. or more. Consequently, the Rsk value of the polishing pad 11 can be set at −0.5 or less.

Then, the film to be polished is polished in step S22. More specifically, the film to be polished held by the top ring 12 is brought into contact with the conditioned polishing pad 11, and slid against the polishing pad 11. The rate of rotation of the top ring 12 is set at, for example, 120 rpm, and the polishing load is set at, for example, 300 gf/cm². Also, the slurry supply nozzle 12 supplies the slurry at a flow rate of 100 cc/min. The slurry contains cerium oxide (DLS2 manufactured by Hitachi Chemical) as abrasive grains and ammonium polycarboxylate (TK75 manufactured by Kao).

By thus polishing the film to be polished by bringing its surface into contact with the surface of the rotating polishing pad 11 having an Rsk value of −0.5 or less, the number of scratches on the surface of the polished film can be reduced. The basis for this will be described later.

Note that the Rsk value on the surface of the polishing pad 11 is desirably −0.5 or less, and more desirably, −1.0 or less. However, the Rsk value on the surface of the polishing pad 11 is not limited to this, and need only be negative. As will be described later, when the surface temperature of the polishing pad 11 is raised during conditioning, the Rsk value of the polishing pad 11 decreases (i.e., the Rsk value becomes a negative value having a large absolute value). That is, the Rsk value is desirably decreased by raising the surface temperature of the polishing pad 11 during conditioning. However, the Rsk value of the polishing pad 11 may only be a negative value even when the surface temperature of the polishing pad 11 is less than 23° C.

FIG. 4 is a view for explaining the Rsk value.

The Rsk value (roughness curve skewness value) indicates the relativity of a probability density distribution with respect to the average line of a surface roughness profile.

When the probability density distribution is biased below the average line of the surface roughness profile as indicated by (a) in FIG. 4, the Rsk value is positive. In this state, the number of projecting portions is large, and that of flat portions is small.

On the other hand, when the probability density distribution is biased above the average line of the surface roughness profile as indicated by (b) in FIG. 4, the Rsk value is negative. In this state, the number of projecting portions is small, and that of flat portions is large.

That is, the surface is smoother when the Rsk value is negative than when it is positive.

[Basis of CMP Conditions]

The basis of the CMP conditions according to this embodiment will now be explained with reference to FIGS. 5 and 6.

First, a polishing experiment for checking the relationship between the Rsk value on the surface of the polishing pad 11 and the number of scratches on the surface of a film to be polished was conducted.

FIG. 5 is a graph showing the relationship between the Rsk value on the surface of the polishing pad 11 and the number of scratches on the surface of the film to be polished in the polishing experiment. The Rsk value herein mentioned was calculated from the roughness measured by a high-field laser microscope, for example, HD100D (manufactured by Lasertec). The number of scratches was counted by a KLA2815 (manufactured by KLA-Tencor, SEM Review) after the surface of the film to be polished was lightly etched with diluted hydrofluoric acid after CMP.

As shown in FIG. 5, when the surface of a film to be polished is polished by bringing the surface into contact with the surface of the polishing pad 11, there is a positive correlation (correlation coefficient=0.71) between the Rsk value on the surface of the polishing pad 11 and the number of scratches produced by the polishing on the surface of the film to be polished. In other words, the number of scratches on the surface of the film to be polished increases when the Rsk value of the polishing pad 11 increases, and decreases when the Rsk value decreases.

Also, as the Rsk value on the surface of the polishing pad 11 increases toward the negative side (as the absolute value of the negative Rsk value increases), the number of scratches on the surface of the film to be polished decreases, and the variation in number decreases. Especially when the Rsk value on the surface of the polishing pad 11 is −0.5 or less, more desirably, −1.0 or less, the number of scratches on the surface of the film to be polished further decreases, and the variation in number further decreases.

As described above, the number of scratches on the surface of the film to be polished can be decreased by polishing the film by setting the Rsk value on the surface of the polishing pad 11 at a negative value having a large absolute value. Accordingly, the Rsk value on the surface of the polishing pad 11 is desirably set at a negative value having a large absolute value by conditioning.

Then, a conditioning experiment for checking the relationship between the surface temperature and Rsk value of the polishing pad 11 was conducted. In this experiment, the surface temperature of the polishing pad 11 to be measured by the inlet temperature measurement device 16 was adjusted by controlling the dressing liquid to be supplied from the dressing liquid supply nozzle 14 in the above-described CMP apparatus. The conditioning experiment was conducted under the following conditions.

Polishing pad: Polyurethane (Shore D hardness=60, modulus of elasticity=400 MPa)
Turntable rate of rotation: 20 rpm
Dresser: Diamond roughness=#100 (available from Asahi Diamond)
Dresser load: 200 hPa
Dresser rate of rotation: 20 rpm

Conditioning experiments were conducted for 60 sec by using pure water as the dressing liquid, and setting the supply temperature at 5, 23 (room temperature), and 65° C. In these conditioning experiments, the surface temperatures of the polishing pad 11 measured by the inlet temperature measurement device 16 were 9, 23, and 41° C.

FIG. 6 is a graph showing the relationship between the surface temperature and Rsk value of the polishing pad 11 in the conditioning experiment.

As shown in FIG. 6, when conditioning the surface of the polishing pad 11 by the dresser 15, there is a negative correlation between the surface temperature of the polishing pad 11 during the conditioning, and the resultant Rsk value of the polishing pad 11. In other words, the Rsk value of the polishing pad 11 decreases when the surface temperature of the polishing pad 11 rises, and increases when the surface temperature decreases. More specifically, the Rsk values of the polishing pad 11 are −0.43, −0.56, and −0.78 when the surface temperatures of the polishing pad 11 are 9, 23, and 41° C., respectively.

As described above, the Rsk value on the surface of the polishing pad 11 is desirably set at a negative value having a large absolute value by conditioning. The Rsk value on the surface of the polishing pad 11 can be set at a negative value having a large absolute value by increasing the surface temperature of the polishing pad 11 during conditioning. For example, when supplying pure water in conditioning, the Rsk value on the surface of the polishing pad 11 can sufficiently be set at −0.5 or less by setting the surface temperature of the polishing pad 11 at 23° C. or more.

On the other hand, the polishing rate of the polishing pad 11 during conditioning depends on the surface temperature of the polishing pad 11. The polishing rate decreases when the surface temperature of the polishing pad 11 rises, and increases when the surface temperature decreases. More specifically, the polishing rates of the polishing pad 11 during conditioning are 0.9, 0.5, and 0.05 μm/min when the surface temperatures of the polishing pad 11 are 9, 23, and 41° C., respectively. This is so probably because when the surface temperature of the polishing pad 11 rises, the polishing pad 11 softens (the modulus of elasticity decreases), and polishing becomes difficult. That is, the useful life of the polishing pad 11 can be prolonged by raising the surface temperature of the polishing pad 11.

As described above, when performing conditioning by raising the surface temperature of the polishing pad 11, it is possible to set the Rsk value of the polishing pad 11 at a negative value having a large absolute value, and decrease the polishing rate of the polishing pad 11.

Note that the surface temperature of the polishing pad 11 is the inlet temperature of the polishing pad 11 measured by the inlet temperature measurement device 16, and can be measured at any point on the surface of the polishing pad 11 when the dressing liquid is supplied on the entire surface of the polishing pad 11.

[Effects]

In the CMP method of the semiconductor device manufacturing method according to the abovementioned embodiment, after the surface of the polishing pad 11 is conditioned at a high temperature, a film to be polished is polished by bringing its surface into contact with the surface of the polishing pad 11. This can achieve the following effects.

Since the surface of the polishing pad 11 is conditioned at a higher temperature, the Rsk value on the surface of the polishing pad 11 can be set at a negative value having a larger absolute value. For example, when supplying pure water in conditioning, the Rsk value on the surface of the polishing pad 11 can be set at −0.5 or less by setting the surface temperature of the polishing pad 11 at 23° C. or more. When a film to be polished is polished by bringing its surface into contact with the surface of the polishing pad 11 having this negative Rsk value, the number of scratches on the surface of the film to be polished after CMP can be reduced. Consequently, it is possible to suppress the decrease in device yield and reliability.

It is also possible to decrease the polishing rate of the polishing pad 11 by conditioning the surface of the polishing pad 11 at a higher temperature. This makes it possible to prolong the service life of the polishing pad 11, and reduce the cost of the CMP step.

Application Example

An application example of the semiconductor device manufacturing method according to this embodiment will be explained below with reference to FIGS. 7 and 8. In this example, a method of manufacturing an STI structure in a semiconductor device will be explained.

FIGS. 7 and 8 are sectional views showing semiconductor device STI manufacturing steps according to the embodiment.

First, as shown in FIG. 7, a silicon nitride film 21 functioning as a stopper film is formed on a semiconductor substrate 20. After that, STI patterns 22 are formed in the semiconductor substrate 20 by using a silicon oxide film or the like as an etching mask. Note that it is also possible to form, for example, a silicon oxide film between the semiconductor substrate 20 and silicon nitride film 21.

Then, a silicon oxide film 23 is formed on the entire surface by, for example, high-density plasma chemical vapor deposition (CVD). In this step, the silicon oxide film 23 is formed outside the STI patterns 22.

Subsequently, as shown in FIG. 8, CMP is performed using the silicon oxide film 23 as a film to be processed, thereby polishing the surface of the film. The embodiment is applied to this CMP step. That is, after conditioning is performed such that the Rsk value on the surface of the polishing pad 11 becomes a negative value, the silicon oxide film 23 is polished by bringing its surface into contact with the surface of the polishing pad 11. Consequently, the silicon oxide film 23 outside the STI patterns 22 is removed, and an STI structure is formed.

The present embodiment is not limited to this, and the CMP method according to this embodiment is applicable to CMP performed for various metal materials and various insulating materials as films to be processed.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. A semiconductor device manufacturing method comprising:

forming a film to be polished on a semiconductor substrate; and

performing a CMP method on the film to be polished,

wherein the CMP method includes polishing the film to be polished by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

2. The method of claim 1, wherein the Rsk value is not more than −0.5.

3. The method of claim 1, wherein the Rsk value is not more than −1.0.

4. The method of claim 1, wherein before the polishing the film to be polished, the CMP method further comprises conditioning the polishing pad by bringing a dresser into contact with the surface of the polishing pad while supplying pure water to the surface of the polishing pad.

5. The method of claim 4, wherein a surface temperature of the polishing pad is not less than 23° C. in the conditioning the polishing pad.

6. The method of claim 5, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

the surface temperature of the polishing pad is an inlet temperature of the polishing pad on an upstream side in a rotating direction with respect to the dresser.

7. The method of claim 5, wherein the surface temperature of the polishing pad is controlled by a supply temperature and supply flow rate of the pure water.

8. The method of claim 4, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

a rate of rotation of the polishing pad is 10 (inclusive) to 110 (inclusive) rpm.

9. The method of claim 4, wherein

the dresser is rotated in the conditioning the polishing pad, and

a rate of rotation of the dresser is 10 (inclusive) to 110 (inclusive) rpm.

10. The method of claim 4, wherein a load of the dresser to be brought into contact with the surface of the polishing pad is 50 (inclusive) to 300 (inclusive) hPa.

11. The method of claim 1, wherein the polishing pad contains polyurethane as a main material, and has a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa.

12. The method of claim 1, wherein the film to be polished is a silicon oxide film to be used as an STI structure.

13. A chemical mechanical polishing method comprises polishing a film to be polished formed on a substrate by bringing a surface of the film to be polished into contact with a surface of a polishing pad having a negative Rsk value.

14. The method of claim 13, wherein the Rsk value is not more than −0.5.

15. The method of claim 13, wherein the Rsk value is not more than −1.0.

16. The method of claim 13, further comprising, before the polishing the film to be polished, conditioning the polishing pad by bringing a dresser into contact with the surface of the polishing pad while supplying pure water to the surface of the polishing pad.

17. The method of claim 16, wherein a surface temperature of the polishing pad is not less than 23° C. in the conditioning the polishing pad.

18. The method of claim 17, wherein

the polishing pad is rotated in the conditioning the polishing pad, and

the surface temperature of the polishing pad is an inlet temperature of the polishing pad on an upstream side in a rotating direction with respect to the dresser.

19. The method of claim 17, wherein the surface temperature of the polishing pad is controlled by a supply temperature and supply flow rate of the pure water.

20. The method of claim 13, wherein the polishing pad contains polyurethane as a main material, and has a Shore D hardness of 50 (inclusive) to 80 (inclusive) and a modulus of elasticity of 200 (inclusive) to 700 (inclusive) MPa.