CN102789974B - Method for Improving Chemical Mechanical Planarization Uniformity of Shallow Trench Isolation - Google Patents

Abstract

The invention discloses a method for improving the chemical mechanical planarization uniformity of the shallow trench isolation, comprising: depositing and forming a silicon oxide isolation layer in the shallow trench, the silicon oxide isolation layer having a protruding part and a concave part; performing ion implantation , changing the crystallization state of the protruding portion; performing chemical mechanical polishing on the silicon oxide isolation layer until the stop layer is exposed. According to the method for improving the chemical mechanical planarization uniformity of the shallow trench isolation of the present invention, the combination of ion implantation and silicon oxide CMP technology is used, and the ion implantation treatment is performed on the protruding part of the silicon oxide to improve the impact of the CMP polishing liquid on the protruding parts. Material removal rate for partial silicon oxide. In the STI CMP process, the purpose of reducing the thickness drop of the oxide layer above the shallow trench isolation region and the non-isolation region is achieved, thereby improving the planarization uniformity of the STICMP process, that is, reducing the degree of depression defects.

Description

Method for Improving Chemical Mechanical Planarization Uniformity of Shallow Trench Isolation

technical field

The invention relates to a method for manufacturing a semiconductor device, in particular to a method for improving the chemical mechanical planarization uniformity of shallow trench isolation.

Background technique

Since the introduction of shallow trench isolation (STI) technology from the 0.25um technology node, high-density isolation of devices has become possible. As technology nodes continue to shrink, in order to improve device density and isolation effects, the aspect ratio (AR) of the shallow trench itself continues to increase. High-density plasma chemical vapor deposition (HDP-CVD) is the mainstream technique for filling shallow trenches. This technology overcomes the possible sealing problem at the top of the trench through the cyclic process of deposition and etching, and completes the filling of the large AR trench structure. The effect after silicon oxide filling is shown in Figure 1. Among them, a pad oxide layer and a silicon nitride layer 2 are sequentially formed on the silicon substrate 1, and a plurality of STIs with a large AR are formed by etching. After these STIs are filled with HDP-CVD silicon dioxide, the deposited silicon oxide and the pad oxide layer The silicon dioxide is connected to form the silicon oxide layer 3 .

As the shallow trench aspect ratio (aspect ratio) continues to increase, after HDP-CVD, the silicon oxide thickness gap between the shallow trench isolation region and the non-shallow trench isolation region (active region) becomes larger and larger , which poses a great challenge to the control of the internal uniformity of the wafer chip in the next shallow trench isolation chemical mechanical planarization (STI CMP) process. Due to the large silicon oxide thickness drop (the height difference at the top of the silicon oxide layer 3 in FIG. 1 is, for example, ), in the STI CMP process, this thickness difference cannot be eliminated directly by the CMP process, and will be inherited until the end of the CMP process, causing part of the silicon oxide in the shallow trench to be worn away, forming a dishing defect, and causing the electrical performance of the device decline, or even a reduction in yield, see Figure 2.

All in all, when the current HDP-CVD fills the STI with high AR, the large silicon oxide thickness difference reduces the CMP uniformity and causes device defects.

Contents of the invention

Therefore, the object of the present invention is to improve the STI CMP uniformity to improve the reliability of the device.

The invention provides a method for improving the chemical mechanical planarization uniformity of the shallow trench isolation, comprising: depositing and forming a silicon oxide isolation layer in the shallow trench, and the silicon oxide isolation layer has a protruding part and a concave part; ion implantation, changing the crystal state of the protruding part; performing chemical mechanical polishing on the silicon oxide isolation layer until the stop layer is exposed.

Wherein, the step of ion implantation includes coating photoresist on the silicon oxide isolation layer, exposing the protruding part after exposure and development, and retaining the photoresist at the recessed part, so that the remaining photoresist Glue is used as a mask for vertical ion implantation. Wherein, the mask used for the exposure and development is complementary to the mask used for forming the shallow trench, and the photoresist is removed after the vertical ion implantation.

Wherein, the step of ion implantation includes determining an implantation inclination angle θ according to the height H of the protruding portion and the width L of the shallow trench, and performing oblique ion implantation on the protruding portion with the inclination angle θ. Wherein, after performing the oblique ion implantation, a second oblique ion implantation to the protruding portion is further included, and the second oblique ion implantation is symmetrical to the oblique ion implantation. Wherein, the inclined ion implantation and/or the second inclined ion implantation are realized by rotating the wafer or rotating the implantation source.

Wherein, the types of ion implantation include H, C, N, B, BF ₂ , In, P, As, Sb and combinations thereof. Wherein, the ion implantation dose is 1×10 ¹⁴ to 5×10 ¹⁵ /cm ² , and the implantation energy is 10KeV to 150KeV. Wherein, the chemical mechanical polishing uses a SiO2-based grinding liquid or a CeO2-based grinding liquid. Wherein, the chemical mechanical polishing uses a hard polishing pad or a soft polishing pad.

According to the method for improving the chemical mechanical planarization uniformity of the shallow trench isolation of the present invention, the combination of ion implantation and silicon oxide CMP technology is used, and the ion implantation treatment is performed on the protruding part of the silicon oxide to improve the impact of the CMP polishing liquid on the protruding parts. Material removal rate for partial silicon oxide. In the STI CMP process, the purpose of reducing the thickness drop of the oxide layer above the shallow trench isolation area and the non-isolation area is achieved, thereby improving the planarization uniformity of the STI CMP process, that is, reducing the degree of depression defects.

The stated objects of the invention, as well as other objects not listed here, are met within the scope of the independent claims of the present application. Embodiments of the invention are defined in the independent claim and specific features are defined in its dependent claims.

Description of drawings

Describe technical scheme of the present invention in detail below with reference to accompanying drawing, wherein:

Figure 1 shows a schematic cross-sectional view of an STI filled with high AR by HDP-CVD in the prior art;

Fig. 2 has shown the schematic cross-section of the STI CMP of prior art;

3 to 5 show schematic cross-sectional views of various steps of vertical ion implantation according to an embodiment of the present invention;

6 and 7 show schematic cross-sectional views of various steps of inclined ion implantation according to another embodiment of the present invention; and

8 and 9 show schematic cross-sectional views of various steps of CMP after ion implantation according to the present invention.

Detailed ways

The features and technical effects of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and in conjunction with schematic embodiments, and a method for improving the uniformity of STI CMP is disclosed. It should be pointed out that similar reference numerals represent similar structures, and the terms "first", "second", "upper", "lower" and the like used in this application can be used to modify various device structures or process steps . These modifications do not imply spatial, sequential or hierarchical relationships of the modified device structures or process steps unless otherwise specified.

After a large number of experiments and data analysis, the applicant found that after the ion implantation of silicon oxide, its chemical bond and crystallization state are destroyed, so the chemical corrosion effect of the polishing liquid on the ion implanted silicon oxide will be greatly enhanced, thereby increasing its material removal rate . Therefore, the main idea of the present invention is to increase the material removal rate of the silicon oxide on the protruding part by the CMP slurry by performing ion implantation on the protruding part of the silicon oxide. In the STI CMP process, the purpose of reducing the thickness drop of the oxide layer above the shallow trench isolation area and the non-isolation area is achieved, thereby improving the planarization uniformity of the STI CMP process, that is, reducing the degree of depression defects.

Example 1

3 to 5 are schematic cross-sectional views showing various steps of vertical ion implantation to increase silicon oxide removal rate according to Embodiment 1 of the present invention.

First, referring to Figure 3, a pad silicon oxide layer and a silicon nitride layer 2 are formed on the substrate 1, and a high AR STI is formed by photolithography/etching, and then HDP-CVD is used to fill the high AR STI with silicon dioxide, and the filled The silicon dioxide is bonded with the pad oxide layer to form a silicon oxide isolation layer 3 . After the silicon oxide isolation layer 3 is deposited, the entire wafer is coated with photoresist; the reverse mask (that is, complementary to the exposure mask used to form STI) with shallow trench isolation is exposed, developed, The silicon oxide in the protruding part of the non-shallow trench region is exposed, and the photoresist 4 in the concave part is retained, as shown in the grid part in FIG. 3 .

Next, referring to FIG. 4 , according to the height of the protruding portion of the silicon oxide 3 , select appropriate ion implantation conditions, and perform vertical ion implantation on the protruding portion, as shown by the arrow in FIG. 4 . The ion implantation depth is equal to or less than the silicon oxide drop thickness. Specifically, for the silicon oxide thickness drop of the present invention is When , the implanted ion species include but not limited to at least one of H, C, N, B, BF ₂ , In, P, As or Sb and combinations thereof, and the implanted dose is 1×10 ¹⁴ to 5×10 ¹⁵ /cm ² , the implantation energy is 10KeV to 150KeV. After the vertical ion implantation, the protruding area at the top of the silicon oxide layer 3, that is, the non-STI area, is exposed to the implanted ion atmosphere, and its chemical bond and crystallization state are destroyed, thus greatly enhancing the chemical resistance of the polishing solution to the ion implantation treatment of silicon oxide. Corrosive action, thereby increasing its material removal rate.

Again, referring to FIG. 5 , after the vertical ion implantation, the photoresist is removed by wet etching or dry and wet etching, and the wafer is dried. Wet degumming can use acetone and aromatic organic solvents, as well as sulfuric acid and hydrogen peroxide. Dry stripping can use oxygen-containing plasma reactive etching to remove photoresist, oxidize organic photoresist into gas and pump it away by vacuum system. In the protruding silicon oxide layer 3 in FIG. 5 , the dotted part represents the chemical bond and crystallization state destruction caused by ion implantation.

After ion implantation changes the crystalline state of the silicon oxide layer, CMP is continued to planarize the silicon oxide layer, see FIGS. 8 and 9 . The ion-implanted wafer is subjected to silicon oxide CMP treatment, as shown in FIG. 8 , using a rotating polishing pad to planarize the silicon oxide layer 3 under the action of a polishing liquid until the silicon nitride layer 2 serving as a CMP stop layer is exposed. CMP can use a hard polishing pad or a soft polishing pad, such as a 0.08-inch thick Rodel IC1000 and a 0.05-inch thick SUBA IV pad, the grinding disc speed is about 25-90r/min, and the pressure is 3-8psi. The grinding liquid of CMP can be SiO ₂ base grinding liquid, also can be CeO ₂ base grinding liquid, the flow rate of grinding liquid is about 50-125mL/min, KOH can be added in it to soften silicon oxide. Since the chemical bond and crystalline state of the silicon oxide in the protruding part are destroyed after ion implantation, the chemical corrosion effect of the polishing liquid on the protruding silicon oxide will be enhanced, and the removal rate of the protruding silicon oxide in the CMP process will be increased, thereby During the grinding process, the thickness drop will not be inherited to the silicon oxide in the shallow trench, and the depression of the silicon oxide in the shallow trench will be reduced. See Figure 9. It can be seen that the final STI flatness is better than that shown in Figure 2. Results obtained by conventional CMP methods.

Example 2

FIG. 6 to FIG. 7 show cross-sectional schematic diagrams of various steps of inclined ion implantation to increase silicon oxide removal rate according to Embodiment 2 of the present invention.

Referring to FIG. 6, after the silicon oxide isolation layer 3 is deposited, the inclination angle of the implantation is firstly determined according to the height H and spacing L of the pattern. In order to ensure that silicon oxide is not implanted in the recess during ion implantation, it is necessary to determine the implantation inclination angle θ, the expression of which is θ≈arctan(H/L), that is, the implantation inclination angle θ is approximately equal to arctan(H/L), where H and L can be obtained by layout design and measurement methods. Specifically, in the present invention, H is the difference in thickness of the silicon oxide layer, which is L is the width of the shallow trench STI, for example After determining the implantation inclination angle, perform inclined ion implantation, the implanted ion species includes but not limited to at least one of H, C, N, B, BF ₂ , In, P, As or Sb and combinations thereof, and the implanted dose is 1 ×10 ¹⁴ to 5×10 ¹⁵ /cm ² , and the implantation energy is 10KeV to 150KeV. Due to the reasonable selection of the inclination angle, most of the implanted ions are distributed in the non-STI area, that is, the area where the top of the silicon oxide layer 3 protrudes, and its chemical bonds and crystallization state are destroyed, so the ion implantation process of the polishing liquid will be greatly enhanced. Chemical etching of silicon oxide, thereby increasing its material removal rate.

If the thickness of the silicon oxide in the protruding part is thicker, in order to ensure that the silicon oxide in the protruding part is implanted as fully as possible; from the symmetrical direction, use the same inclination angle and implantation conditions to inject it again, see Figure 7, where the dotted part represents the crystallization state. Change. This step of implantation can be confirmed according to the actual thickness of silicon oxide; if the first implantation can ensure that the protruding part will be reached by the implanted ions, this step of symmetrical implantation is not required; if the first implantation cannot make the protruding part completely covered by the implanted ions Hit, need to take this step symmetrical implantation, the inclination angle θ of symmetrical implantation is the same as above. The first oblique ion implantation and/or the second oblique ion implantation can be achieved by rotating the wafer or rotating the implantation source, so as to ensure that ions are uniformly implanted in the protruding part, so that the crystallization state of the protruding part can be changed.

Subsequently, referring to FIG. 8 and FIG. 9 , similar to Embodiment 1, after the ion implantation changes the crystalline state of silicon oxide, CMP is continued to planarize the STI.

According to the method for improving the chemical mechanical planarization uniformity of the shallow trench isolation of the present invention, the combination of ion implantation and silicon oxide CMP technology is used, and the ion implantation treatment is performed on the protruding part of the silicon oxide to improve the impact of the CMP polishing liquid on the protruding parts. Material removal rate for partial silicon oxide. In the STI CMP process, the purpose of reducing the thickness drop of the oxide layer above the shallow trench isolation area and the non-isolation area is achieved, thereby improving the planarization uniformity of the STI CMP process, that is, reducing the degree of depression defects.

While the invention has been described with reference to one or more exemplary embodiments, it will be apparent to those skilled in the art that various suitable changes and equivalents can be made in the process schemes without departing from the scope of the invention. In addition, many modifications, possibly suited to a particular situation or material, may be made from the disclosed teaching without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode for carrying out this invention, but that the disclosed device structures and methods of making the same will include all embodiments falling within the scope of the invention .

Claims (10)

1. improve the method for shallow trench isolation from chemical-mechanical planarization uniformity, comprising:

In shallow trench, deposit forms silica separator, and described silica separator has projection and sunk part;

Perform ion implantation, the ion implantation degree of depth is equal to or less than silica drop thickness, changes the crystalline state of described projection, and its chemical bond and crystalline state are destroyed;

Chemico-mechanical polishing is performed, until expose stop-layer to described silica separator.

2. the method for claim 1, wherein the step of described ion implantation comprises, described silica separator applies photoresist, expose described projection after exposure imaging, retain the photoresist of described depressed part office, with the photoresist retained for mask carries out vertical ion injection.

3. method as claimed in claim 2, wherein, the mask plate that described exposure imaging uses is complementary with the mask plate forming described shallow trench, and vertical ion removes described photoresist after injecting.

4. the method for claim 1, wherein the step of described ion implantation comprises, and determines to inject inclination angle theta according to the height H of described projection and the width L of described shallow trench, performs angle-tilt ion inject with described inclination angle theta to described projection.

5. method as claimed in claim 4, wherein, after the described angle-tilt ion of execution is injected, also comprise and injecting the second time angle-tilt ion of described projection, described second time angle-tilt ion is injected and is injected symmetry with described angle-tilt ion.

6. method as claimed in claim 5, wherein, realizes described angle-tilt ion by rotating wafer or rotation injection source and injects and/or the injection of described second time angle-tilt ion.

7. the method for claim 1, wherein the kind of described ion implantation comprises H, C, N, B, BF ₂, In, P, As, Sb and combination thereof.

8. the method for claim 1, wherein the dosage of described ion implantation is 1 × 10 ¹⁴/ cm ²to 5 × 10 ¹⁵/ cm ², Implantation Energy is 10KeV to 150KeV.

9. the method for claim 1, wherein described chemico-mechanical polishing uses SiO ₂base lapping liquid or CeO ₂base lapping liquid.

10. the method for claim 1, wherein described chemico-mechanical polishing uses hard polishing pad or soft polishing pad.