JPH0922888A - Abrasive, polishing method, and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method which includes a process in which a conductor pattern is formed so that a recessed section formed in an insulating layer can be filled by polishing a conductor layer deposited on the insulating layer and which can minimize the erosion of a seam in the conductor pattern which occurs when the conductor layer is polished. SOLUTION: A conductor layer is selectively polished against an insulating layer with an abrasive containing MnO2 as abrasive grains without using any liquid oxidizing agent and remaining MnO2 is removed by dissolving the MnO2 through acid treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to semiconductor device manufacturing, and more particularly to a method of manufacturing a semiconductor device including a polishing step.

[0002]

2. Description of the Related Art In semiconductor devices, especially semiconductor integrated circuits,
A multilayer wiring structure is generally used in which a wiring structure in which a wiring pattern is embedded on an insulating layer formed on a substrate is multilayered. In such a multilayer wiring structure, since another wiring structure is formed on the first lower wiring structure, each wiring structure is required to have a flat surface.

Therefore, conventionally, when a multilayer wiring structure is formed, a contact hole or a wiring groove is formed on an insulating layer, and a metal layer is formed on the insulating layer so as to fill the contact hole or the wiring groove. It has been practiced to deposit and then remove such metal layer by polishing until the surface of the insulating layer is exposed to form a flat wiring structure. Since this wiring structure has a flat upper main surface, the next wiring structure can be easily formed thereon.

A conventional method of manufacturing a semiconductor device including such a polishing step will be described below with reference to FIGS. Referring to FIG. 4A, a MOS transistor is formed on, for example, a p-type doped Si substrate 1 corresponding to an active region 1A defined by a field oxide film 1a formed on the substrate 1. To be done. More specifically, the MOS transistor includes an n ⁺ -type diffusion region 1b formed on the surface of the active region 1A and a MOS region formed on the surface of the active region 1A from the diffusion region 1b.
The transistor includes a diffusion region 1c formed by being separated by a channel region 1d of a transistor, and a gate electrode 2 formed on the channel region 1d with a gate oxide film (not shown) interposed therebetween. Sidewall insulating films 2a and 2b are formed on the sidewalls of the electrode 2. The diffusion regions 1b and 1c function as a source region and a drain region of a MOS transistor, respectively.

In the process of FIG. 4A, the MOS transistor
Embedded in the transistor _TwoInterlayer insulation consisting of
The film 3 has a thickness of typically 50 nm by a CVD method or the like.
Deposited to a thickness of the order of magnitude. As a result, the gate electrode and
And the diffusion regions 1b and 1c are covered with the insulating film 3.
You. However, as shown in FIG. 4A, the surface of the insulating film 3
Have irregularities corresponding to the gate electrode 2.

Next, in the step of FIG. 4B, the surface of the insulating film 3 is uniformly polished, and as a result, the surface of the insulating film 3 is flattened. Further, in the step of FIG. 5C, the insulating film 3 is patterned by photolithography using a resist (not shown), and as a result, the insulating film 3 is formed in the insulating film 3 corresponding to the diffusion region 1b. Contact hole 3a exposing the surface of region 1b is formed. Furthermore, FIG.
In the process of (D), W and A are formed on the structure of FIG.
The conductor layer 4 made of a metal or alloy such as l or Cu is deposited to a uniform thickness by, for example, the CVD method. as a result,
The conductor layer 4 fills the contact hole 3a and makes electrical contact with the diffusion region 1b in the contact hole. As described above, in the structure of FIG. 5D, the conductor layer 4 fills the contact hole 3a,
A recess 4a appears on the surface of the conductor layer 4 corresponding to the contact hole 3a. In other words, the surface of the conductor layer 4 has irregularities.

Then, in the next step of FIG. 6E, the conductor layer 4 is uniformly polished to obtain a structure in which the surface of the insulating film 3 is flat as shown in FIG. 6E. The polishing of the conductor layer 4 selectively acts on the metal forming the conductor layer 4, and stops when the upper main surface of the insulating layer 3 is exposed. As a result, a conductor plug 4b contacting the diffusion region 1b is formed so as to fill the contact hole 3a.
As a result of the flattening by polishing, the upper main surface of the conductor plug 4b coincides with the upper main surface of the insulating film 3.

Next, in the step of FIG. 6 (F), another insulating film 5 made of SiO ₂ or the like is deposited on the flattened structure of FIG. 6 (E), and then the step of FIG. 7 (G). Is patterned by photolithography with the conductive plug 4
A groove 5a exposing b is formed. Further, in the step of FIG. 7 (H), another conductor layer 6 made of a metal or alloy such as W, Al, Cu is deposited on the structure of FIG. 7 (G), so that it corresponds to the groove 5a. A recess 6a is formed in the conductor layer 6 as shown in FIG. 7 (H).

Further, the conductor layer 6 is polished in the step of FIG. 8 (I) to obtain the flattened structure shown in FIG. 8 (I). In the structure of FIG. 8I, the groove in the insulating film 5 is filled with the conductor pattern 6b forming a part of the conductor layer 6. Further, another insulating layer 7 is deposited on the structure in the step of FIG. In such a structure, various wiring patterns can be formed on the insulating layer 7 as needed.

[0010]

In the above-described semiconductor device manufacturing process, the polishing step for the conductor layer 4 or 6 in FIG. 6 (E) or FIG. 8 (I) is performed by using abrasive grains made of α-Al ₂ O _3. And an oxidizer such as H ₂ O ₂ and the like, and a polishing cloth made of urethane resin or the like. For example, as such an abrasive, the abrasive supplied by Rodel-Nitta under the trade name MSW1000 is generally used. In such a polishing step, the oxidizing agent oxidizes the conductor layer, and the formed oxide is ground and removed by the abrasive grains.

For example, a conductor layer made of W is used as the α-Al.
_TwoO_ThreeWhen polishing with abrasive grains, H _TwoO_TwoBy the acid of W
Compound W_xO_yAre formed, and such oxides are formed by the abrasive grains.
It is scraped. However, an abrasive containing such an oxidizing agent
When used for polishing a conductor layer such as W, the oxidant is
In the conductor layer 4 filling the recess, for example, the recess 4a, the conductor
The seam or seam 4c formed during the deposition of layer 4
The presence of such oxidants as a result
By the polishing step performed below, the seam 4c is
The state shown in FIG. 9 (A) changes to the state shown in FIG. 9 (B).
There is a problem that it expands due to the etching action of the agent
I do. As a result, the enlarged portion is formed in the central portion of the conductor plug 4b.
Large and deep recesses are formed corresponding to the seams 4c
The diffusion region 1 in the contact hole 3a.
The contact between b and the conductor pattern 6b becomes uncertain.
Problems arise. Formed on such a conductor plug during polishing
In particular, the size of the contact hole 3a is 0.5.
A semiconductor device having a high integration density of μm or less
Devices and integrated circuits suffer particularly serious reliability degradation.
Bring. The seam 4c has a large aspect ratio.
When filling the contact hole by depositing the conductor layer
In the contact hole from the side wall surface of the contact hole
The conductor layer that grows toward the center is the contact hole.
Formed by abutting in the center of the
It is considered to include. Therefore, the seam 4c
Is H_TwoO_TwoEasily receives etching with an oxidizing agent such as
I can.

Therefore, it is a general object of the present invention to provide a new and useful polishing agent, abrasive grains, polishing method, and semiconductor device manufacturing method that solve the above problems. A more specific object of the present invention is to provide an abrasive containing no oxidizing agent, or an abrasive grain that does not need to be used in combination with an oxidizing agent, a polishing method using these, or a method for manufacturing a semiconductor device using these. To do.

[0013]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above problems by using MnO ₂ or M as described in claim 1.
With an abrasive containing abrasive grains containing nO ₂ as a main component, or as described in claim 2, the grain size of the abrasive grains is 10 μm.
The method according to claim 1, which is characterized by the following, or the method according to claim 3, wherein an abrasive containing abrasive grains of MnO ₂ is used, or Item 4, forming an insulating layer on a substrate; forming a recess in the insulating layer; depositing a conductor layer on the insulating layer so as to fill the recess; In a method of manufacturing a semiconductor device, including a polishing step of polishing the conductor layer until the insulating layer is exposed, the polishing step is performed using an abrasive containing MnO ₂ as abrasive grains. According to a method of manufacturing a semiconductor device or as described in claim 5, further comprising a cleaning step of cleaning the substrate with an acid, wherein the cleaning step is performed after the polishing step. Semi conductor according to item 4 The method for manufacturing a semiconductor device according to claim 5, wherein the cleaning step is performed by a method for manufacturing a body device, or the cleaning step is performed by using a mixed solution of the acid and the oxidizing agent. To solve.

According to the inventions of claims 1, 3, and 4,
By using MnO ₂ as abrasive grains in the step of polishing the conductor layer, oxygen in MnO ₂ oxidizes the metal forming the conductor layer. As a result, it is considered that the reaction product thus generated is ground by Mn ₂ O ₃ reduced as a result of the reaction or unreacted MnO ₂ . For example, when the conductor layer is composed of W, the following reaction MnO ₂ + W → Mn ₂ O ₃ + W _x O _y occurs between the abrasive grains and the conductor layer during polishing, and the generated W _x O _y is polished. It is considered to be ground and removed by the cloth and unreacted MnO2. In the present invention, MnO ₂ that performs an oxidizing action is solid, and a liquid oxidizing agent such as H ₂ O ₂ is not used during polishing, so that the oxidizing agent does not enter the seam. Therefore, there is no problem that a defective portion in a fine conductor pattern embedded in an insulator is etched during polishing, such as a seam shown in FIG. High contacts can be formed.

According to a feature of the present invention described in claim 2,
By setting the grain size of the Mn abrasive grains to 10 μm or less,
The size of the recess formed in the fine conductor pattern embedded in the insulator can be minimized. Claim 4
According to the features of the present invention described, the present invention is effective for polishing a conductor used for a wiring pattern of a semiconductor device, and is useful for manufacturing a semiconductor device.

According to a feature of the present invention as set forth in claim 5, after the polishing step, the substrate is treated with an acid such as HCl, H ₂ SO ₄ HN.
By washing with O ₃ or HF, MnO ₂
For example, the reaction MnO ₂ + 2HCl + H ₂ O ₂ → MnCl ₂
+ 2H ₂ O + O ₂ or MnO ₂ + 2HNO ₃ + H
₂ O ₂ → Mn (NO ₃ ) ₂ + H ₂ O + O ₂ or M
nO ₂ + H ₂ SO ₄ + H ₂ O ₂ → MnSO ₄ + 2H ₂ O
+ O ₂ or MnO ₂ + 2HF + H ₂ O ₂ → MnF
₂ + 2H ₂ O + O ₂ dissolves in acid, and as a result, contamination of the substrate by Mn and the amount of residual particles can be minimized. However, in the above reaction, the reaction products MnCl ₂ , Mn (NO ₃ ) ₂ , MnSO ₄ , MnF ₂
Are all water-soluble compounds. Further, although H ₂ O ₂ which is a liquid oxidant is used in the above cleaning process, unlike the polishing process, the concentration of H ₂ O ₂ in the cleaning process is 2% or less (1/25 of the polishing process). In addition, since the cleaning process is completed in a short time, and since the abrasive grains do not grind, the seam of the conductive plug is not substantially eroded by the oxidizing agent.

According to the sixth aspect of the present invention, the cleaning efficiency can be improved by cleaning the substrate with the mixed solution of the acid and the oxidizing agent in the cleaning step. Therefore, according to the present invention, semiconductor devices can be manufactured with high yield. Unlike the polishing process, even if an oxidizer is used in the cleaning process, the conductor plug filling the contact hole is hardly eroded. Therefore, the reliability of the semiconductor device obtained as a result of the cleaning process does not deteriorate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the case where the present invention is applied to the manufacture of a semiconductor device will be described based on Examples.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining an embodiment of the present invention. Referring to FIG. 1, the structure shown is a test piece prepared for verifying the effect of the polishing agent of the present invention. A SiO ₂ layer deposited on a Si substrate 11 to a thickness of about 50 nm by a CVD method. Including 12. A plurality of contact holes 12a and 12b are formed in the layer 12 with various inner diameters D ₁ and D ₂ , and a W layer 13 is deposited to a thickness of about 50 nm so as to fill the contact holes 12a and 12b. The W layer 13 is deposited by, for example, a CVD method, and a recess 13a is formed on the surface thereof so as to correspond to the contact holes 12a and 12b. Furthermore, contact hole 1
In the W plug filling 2a or 12b, the W layer 13
The seam 13b is formed in accordance with the accumulation of. As described above, the seam 13b is formed by the surface of the W layer 13 converging and abutting when the W layer 13 grows inward from the side walls of the contact holes 12a and 12b. Including defects.

The results of experiments conducted by the inventor of the test piece will be described below. In this experiment, the surface of the W layer 13 on the test piece was polished with an abrasive made of a mixture of MnO ₂ and H ₂ O having various particle sizes. However, the proportion of MnO ₂ in the polishing agent was set to about 20% by weight, and polishing was performed using a urethane resin polishing cloth supplied under the trade name SUBA400 from Rodel-Nitta. The pressure during polishing was set in the range of 200 to 700 g / cm ² .

Further, for comparison, the conventional polishing agent was used to polish the W layer 13 of the test piece of FIG. 1 under the same conditions.
The conventional abrasive used is Rodel-Nitta product number MSW.
1000, including abrasive grains made of α-Al2 O3 and potassium phthalate. However, in the case of this conventional example, the abrasive was mixed with H ₂ O ₂ and used.

In this experiment, the effect of the abrasive was evaluated by the W layer 13 on the SiO2 layer 12 in the test piece of FIG.
Is completely removed, overetching is further performed for 2 minutes, and then the depth of the recess formed in the conductor plug filling the contact hole 3a or 12b as shown in FIG. It was performed by observing the cross section by SEM.

FIG. 2 shows the polishing rates of the SiO2 (shown by circles in the figure) without a pattern and the W layer (shown by ● in the figure) deposited by the CVD method with the pressure set at 350 g / cm ² . . As can be seen from FIG. 2, when the particle size is 2 μm or more, the polishing rate of SiO ₂ increases and the polishing rate of W begins to decrease. When the polishing rate of W is high, the polishing throughput is improved. Further, the smaller the polishing rate of SiO _2, the higher the stopper effect. Therefore SiO
_It is better that the polishing rate of ₂ is low and the polishing rate of W is high. It can be seen from FIG. 2 that the particle size is preferably 10 μm or less.

Assuming plug embedding, it can be expected that the larger the particle size, the better because the abrasive will not enter the plug. However, as shown in FIG. 2, it was found by experiment that it was better that the particle size was 10 μm or less. From the above, the abrasive according to the present invention insulates the conductor layer 4 or 6 in the step of FIG. 6E or the step of FIG. 8I in the manufacture of the semiconductor device described in FIGS. It can be seen that it is effective in selectively polishing and removing from the film. As described above, the abrasive containing MnO ₂ abrasive grains according to the present invention selectively acts on W when the grain size is smaller than 10 μm, so that in the step of FIG. When the conductor layer 4 is a W layer, Si under the layer 4
Polishing is automatically stopped when the O ₂ layer 3 is exposed.

On the other hand, when the polishing agent of the present invention is used for manufacturing a semiconductor device, in order to avoid metal contamination by the polishing agent, the polishing agent containing Mn abrasive grains is substantially washed from the substrate after the polishing step by washing. Need to be completely removed. Below, Mn
The cleaning process performed after the polishing process using O ₂ abrasive grains will be described.

In the present invention, the residual MnO ₂ abrasive grains are
Dissolve and remove by washing in various acid solutions. The inventor of the present invention has conducted favorable experiments on the cleaning treatment using various acid solutions described below. Hereinafter, the experiment of the cleaning process performed by the present inventor will be described.

In this experiment, the test piece subjected to the polishing treatment was used.
(A) HCl + H_TwoO_Two+ H_TwoO (1: 1: 48 bodies
(Product ratio); (B) HNO_Three+ H_TwoO_Two+ H_TwoO (1: 1: 48
Volume ratio); (C) H_TwoSO_Four+ H_TwoO_Two+ H_TwoO (1: 1: 4
8); and (D) HF + H_TwoO_Two+ H_TwoTreatment in O (1: 1: 48) for 30 seconds each, followed by scrubber treatment
went. The samples thus obtained are referred to as sample A and test, respectively.
Material B, Sample C, and Sample D. In such samples A to D,
The following reaction MnO_Two+ 2HCl + H_TwoO_Two→ MnCl_Two+ 2H_TwoO + O_Two MnO_Two+ 2HNO_Three+ H_TwoO_Two→ Mn (NO_Three)_Two+ H_TwoO + O_Two MnO_Two+ H_TwoSO_Four+ H_TwoO_Two→ MnSO_Four+ 2H_TwoO + O_Two MnO_Two+ 2HF + H_TwoO_Two→ MnF_Two+ 2H_TwoO + O_Two And a water-soluble reaction product MnCl_Two, Mn
(NO_Three)_Two, MnSO _Four, MnF_TwoIs formed
I am thought.

For comparison, among the test pieces, a sample which was polished with an abrasive containing MnO2 abrasive grains was directly scrubbed without acid treatment, and the α-A.
Samples obtained by directly scrubbing those polished with an l ₂ O ₃ abrasive (Rodel-Nitta MSW1000) were designated as sample E and sample F, respectively.

With respect to the samples A to F thus obtained,
After soaking in HF with a concentration of 0.5% for 20 seconds,
Metal contamination and residual particles were evaluated. The results are shown in the table below.

[0030]

[Table 1]

As described above, in each of the samples A to D to which the cleaning process of the present invention is applied, the contamination by Mn is negligible, and the number of residual particles is smaller than that of the conventional sample (sample F). Recognize. Further, in the samples A to D,
It can be seen that the metal contamination due to Mn is reduced even in the case where the acid cleaning is omitted (Sample E). This result indicates that the reaction represented by the above chemical formula occurs due to the washing and residual MnO ₂
Are dissolved.

In the above polishing step, the object to be polished, in which the polishing agent of the present invention containing MnO ₂ as abrasive grains is effective, is not limited to the W layer, but includes metals or alloys such as Al and Cu. Be done. FIG. 3 is a flowchart showing a manufacturing process of a semiconductor device including a polishing process according to the present invention.

Referring to FIG. 3, in step S1, the substrate
Alternatively, a device structure is formed on the wafer, and step S2
In this case, an insulating film is deposited to cover such device structure.
Be stacked. This insulating film is, for example, as shown in FIG.
Deposited on the surface by CVD method _TwoIt may be a membrane, but for example B
Insulating film of other composition such as SG or BPSG, or SOG
SiO deposited by other methods such as_TwoIt may be a membrane.

In step S3, the insulating film previously deposited in step S2 is patterned to form a concave pattern such as a contact hole or a groove corresponding to the contact hole 3a in FIG. 5C in the insulating film. Further, step S4
Then, a conductor layer corresponding to the conductor layer 4 is deposited on the insulating film so as to fill the concave pattern. Here, the conductor layer is A, which is generally used in semiconductor integrated circuits, in addition to W.
It may be a metal or alloy such as l or Cu.

Next, in step S5, the conductor layer is
With the abrasive containing MnO _{2 according} to the present invention as abrasive grains,
Polish on a normal polishing cloth. In this polishing process, MnO
_{The 2} abrasive grains are used by suspending them in a solvent such as H ₂ O, but in the present invention, an oxidizing agent is not added to the solvent. As a result, at the time of polishing, the seam formed in the conductor layer filling the concave pattern is not eroded by the oxidizing agent and is not polished by the abrasive grains.

Next, in step S6, in step S5
Treat the polished substrate in acid to remove residual MnO2
Dissolve in acid and remove. In this process,
HCl, H_TwoSO_Four, HNO_Three, HF and other acids with oxidants
MnO remaining after mixing _TwoIs dissolved and removed. That
As a result, MnO used as abrasive grains_TwoSubstrate metal contamination by
Are removed, and the number of residual particles is further reduced.

Further, after step S6, another structure may be formed in the next step on the structure thus obtained. Since the structure obtained in step S6 has a clean and flat upper main surface, the next structure can be easily formed thereon. Further, the abrasive grains made of MnO ₂ , the polishing agent containing the abrasive grains, and the polishing method using the polishing agent according to the present invention are not limited to the manufacture of semiconductor devices, and can be applied to general polishing steps. It is useful.

Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to such embodiments, and various modifications and changes can be made within the scope thereof.

[0039]

According to the inventions of claims 1, 3 and 4,
Since a liquid oxidizer that is used together with abrasive grains in a conventional polishing agent is not used in the present invention, such an oxidant penetrates into a defective portion in a conductor pattern forming a contact such as a seam of a conductor plug in a polishing process. Never. Therefore, a highly reliable contact can be formed.

According to a feature of the present invention described in claim 2,
By setting the grain size of the Mn abrasive grains to 10 μm or less,
It is possible to minimize the size of the recesses formed during polishing in the fine conductor pattern embedded in the insulating layer. According to the features of the present invention described in claim 4, the present invention is effective for polishing a conductor used for a wiring pattern of a semiconductor device, and is useful for manufacturing a semiconductor device.

According to a feature of the present invention as set forth in claim 5, after the polishing step, the substrate is treated with an acid such as HCl, H ₂ SO ₄ HN.
By cleaning with O ₃ or HF, M
Contamination due to n and the amount of residual particles can be minimized. According to the feature of the present invention described in claim 6, the cleaning efficiency can be improved by performing the substrate cleaning in the cleaning step with the mixed liquid of the acid and the oxidant, and as a result, the semiconductor device can be manufactured with a high yield. It can be manufactured.
Unlike the polishing process, even if an oxidizer is used in the cleaning process, the conductor plug filling the contact hole is hardly eroded. Therefore, the reliability of the semiconductor device obtained as a result of the cleaning process does not deteriorate.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a test piece used in the present invention.

FIG. 2 is a diagram showing the effect of the present invention.

FIG. 3 is a diagram showing a method for manufacturing a semiconductor device using the polishing process of the present invention.

4A and 4B are views (No. 1) showing a manufacturing process of a conventional semiconductor device.

5 (C) and 5 (D) are views showing a conventional manufacturing process of a semiconductor device (No. 2).

6 (E) and 6 (F) are views (No. 3) showing a conventional manufacturing process of a semiconductor device.

7 (G) and 7 (H) are views showing a conventional semiconductor device manufacturing process (No. 4).

8 (I) and 8 (J) are views showing a conventional semiconductor device manufacturing process (No. 5).

9 (A) and 9 (B) are views showing a problem that has occurred in a conventional polishing process.

[Explanation of symbols]

 1, 11 substrate 1a field oxide film 1b, 1c diffusion region 1d channel region 2 gate electrodes 2a, 2b gate sidewall insulating film 3, 5, 7, 12 insulating film 3a contact hole 4,6 conductor layer 4a recess 4b conductor plug 4c seam 5a groove 6a recess 6b conductor pattern 12a contact hole 13a conductor pattern recess 13b seam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Oishi, Akira Oishi, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Rentaro Taro, 1015, Uedanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited (72) Inventor Kenzo Hanawa 1380-1 Hara City, Ageo City, Saitama Prefecture (72) Inventor Shigeo Ueda 4-12-25 Fujimi, Fukiage Town, Kitadachi-gun, Saitama Prefecture

Claims (6)

[Claims] 1. An abrasive containing MnO ₂ or abrasive grains containing MnO ₂ as a main component. 2. The abrasive according to claim 1, wherein the grain size of the abrasive grains is 10 μm or less. 3. A polishing method using an abrasive containing abrasive grains of MnO ₂ . 4. A step of forming an insulating layer on a substrate; a step of forming a recess in the insulating layer; a step of depositing a conductor layer on the insulating layer so as to fill the recess; And a polishing step of polishing the insulating layer until the insulating layer is exposed, wherein the polishing step is performed using a polishing agent containing MnO ₂ as abrasive grains. Production method. 5. The method of manufacturing a semiconductor device according to claim 4, further comprising a cleaning step of cleaning the substrate with an acid, the cleaning step being performed after the polishing step. 6. The method of manufacturing a semiconductor device according to claim 5, wherein the cleaning step is performed with a mixed solution of the acid and the oxidizing agent.