CN102263030A - A kind of preparation method of trench type power device - Google Patents

Abstract

The embodiment of the invention discloses a method for manufacturing a groove-type power device and relates to the technical field of a semiconductor process. The method is invented for solving the problem of polycrystalline silicon residuals caused by the bulges on the surface of polycrystalline silicon and the polymer residuals in a polycrystalline silicon dry etching process. The method for manufacturing the groove-type power device comprises the following steps: arranging a hard mask layer on a substrate; arranging a transition layer on the hard mask layer; photo-etching the transition layer, thereby forming a groove window; forming a groove in an area corresponding to the groove window on the substrate; filling the polycrystalline silicon in the groove; and grinding the polycrystalline silicon in the area outside the groove in polishing manner. The method can be applied to the fields of manufacturing a semiconductor chip and an integrated circuit.

Description

A kind of preparation method of trench type power device

technical field

The invention relates to the technical field of semiconductor technology, in particular to a preparation method of a trench type power device.

Background technique

Trench power devices have significant advantages such as high breakdown voltage, low on-resistance, and fast switching speed, and have become mainstream power devices in the field of integrated circuits and other fields. The preparation method of existing trench type power device generally comprises the following steps: grow hard mask (Hard mask) layer; Carry out photoetching on hard mask, expose trench region; Form trench (Trench); Carry out polysilicon Deposition, fill trenches; etch back polysilicon by dry etching to remove excess polysilicon; after that, it also includes forming body region; forming source region; forming insulating dielectric layer, contact hole, metal layer and passivation layer, etc. step.

During the preparation process of the aforementioned trench-type power devices, the inventors found that at least the following problems exist in the prior art: the existing preparation methods are likely to cause polysilicon residues. This is because, in the step of etching back polysilicon by dry etching, as shown in Figure 1, the area of polysilicon to be etched is large and thick, so the by-product polymer produced in the etching process is more , as shown in FIG. 2 , may cover some areas on the surface of the polycrystalline layer, causing further normal etching of some areas to be hindered, leaving blocky residues after etching. In addition, due to the thickness of the polycrystalline layer, some point-shaped protrusions will appear on the surface of the polycrystalline silicon during the process of polycrystalline silicon deposition, which will also cause the polycrystalline silicon to be etched back and cannot be etched clean, resulting in polycrystalline silicon residues. However, if polysilicon remains, it will eventually lead to a short circuit between the gate and source of the device structure, resulting in leakage, which will seriously affect the yield.

Contents of the invention

The embodiment of the present invention provides a method for preparing a trench power device, which can effectively solve the problem of polysilicon residues caused by protrusions on the polysilicon surface and polymer residues during polysilicon dry etching.

In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

A method for preparing a trench power device, comprising:

disposing a hard mask layer on the substrate;

disposing a transition layer on the hard mask layer;

performing photolithography on the transition layer to form a trench window;

forming a trench on the substrate in a region corresponding to the trench window;

filling the trench with polysilicon;

The polysilicon in the area outside the trench is ground away by polishing.

After adopting the above-mentioned technical solution, the preparation method of the trench type power device provided by the embodiment of the present invention, by changing the process flow, adding a transition layer before trench etching, and subsequently adopting the polishing method of polysilicon, instead of the current dry polysilicon It solves the polycrystalline residue problem caused by the protrusion of the polycrystalline surface and the polymer residue in the polycrystalline dry etching process, and then solves the gate-source leakage problem of the finished device, greatly improving the yield. In addition, compared with dry etching, polishing is used to further reduce the cost.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is a schematic diagram of the state before performing polysilicon etch-back in the prior art;

2 is a schematic diagram of the state after polysilicon etch-back in the prior art;

Fig. 3 is the process flow chart of the preparation method provided by the embodiment of the present invention;

Fig. 4 (a) is the process flow chart of embodiment one of the present invention;

Fig. 4(b) is an implementation effect diagram corresponding to the process flow shown in Fig. 4(a).

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in FIG. 3, a method for manufacturing a trench-type power device provided by an embodiment of the present invention includes the following steps:

S11, disposing a hard mask layer on the substrate;

S12, disposing a transition layer on the hard mask layer;

S13, performing photolithography on the transition layer to form a trench window;

S14, forming a trench on the substrate in a region corresponding to the trench window;

S15, filling polysilicon into the trench;

S16, polishing away the polysilicon in the area outside the trench by polishing.

The preparation method of the trench type power device provided by the embodiment of the present invention can effectively solve the problem of polysilicon residue caused by protrusions on the surface of polysilicon and polymer residue during polysilicon dry etching.

Wherein, the transition layer deposited in the step S11 will be used as a stop layer for polishing in the subsequent step S16, and a silicon nitride (Si ₃ N ₄ ) layer may be used. Since the physical properties of Si ₃ N ₄ are different from those of polysilicon, the polishing rate is different. Therefore, when the polishing of the area other than the groove is performed in step S16, when the polishing rate monitored by the polishing equipment changes, it can be judged that the groove The polysilicon in the area outside the groove has been polished, that is, in step S16, the polysilicon in the area outside the groove is ground by polishing, and the polishing can be stopped when the polishing rate changes. It should be noted here that transition layers of other materials may also be used, which is not limited here.

Further, the polishing method used in step S16 is preferably chemical mechanical polishing. In chemical mechanical polishing, chemical agents are added at the same time as mechanical polishing, which can react with the object to be polished, so that the polished surface of the object to be polished is smoother, and the chance of polysilicon residue is further reduced.

In addition, the polishing accuracy of different areas may be slightly different. If some areas are less polished, there may be a small amount of polysilicon residue in these areas. Therefore, in order to ensure that the polysilicon in the area outside the trench can be completely removed and avoid polysilicon residue, excessive polishing can be used to remove some of the transition layer, such as the Si ₃ N ₄ layer, that is, the step S16 can be specifically: Polishing is used to grind the polysilicon in areas other than the groove; when the polishing rate changes, the polishing is continued for a certain period of time and then stopped. Wherein, the time for excessive polishing can be flexibly controlled according to the actual situation and the thickness of the transition layer.

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the embodiments of the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be noted here that the following specific examples are only for describing the present invention, but not limiting the present invention.

Embodiment one

This embodiment is a method for preparing a trench type double-diffused metal semiconductor oxide (DMOS, Doubl-Deffused Metel Oxide Semiconductor) field effect transistor, as shown in Figure 4, wherein, Figure 4 (a) is the process flow of this embodiment Fig. 4 (b) is an implementation effect diagram corresponding to the technological process of Fig. 4 (a), comprising the following steps:

S21, growing a SiO ₂ hard mask layer on the Si substrate;

See S21' for the implementation effect of this step.

S22, depositing a Si ₃ N ₄ transition layer on the SiO ₂ hard mask layer;

See S22' for the implementation effect of this step. The Si ₃ N ₄ transition layer will serve as a stop layer for subsequent steps to polish the polysilicon in areas outside the trench.

S23, performing photolithography on the Si ₃ N ₄ transition layer to form a trench window;

See S23' for the implementation effect of this step.

S24, using plasma dry etching to form a trench on the Si substrate in a region corresponding to the trench window;

In this step, first perform dry etching on the Si ₃ N ₄ transition layer and the SiO ₂ hard mask layer corresponding to the trench window, open the hard mask layer and the transition layer, and expose the trench that needs to be formed on the substrate. area; then perform dry etching on the trench area on the Si substrate, that is, the area corresponding to the trench window, to form a trench, and smooth the bottom of the trench, see S24' for the implementation effect.

S25, performing oxidation of the groove wall;

See S25' for the implementation effect of this step.

S26, filling the trench with polysilicon;

See S26' for the implementation effect of this step.

S27, using a chemical mechanical polishing method to grind away the polycrystal in the area outside the trench.

In this step, the degree of polishing will be judged by detecting the polishing rate. Since the polishing rate of Si ₃ N ₄ is different from that of polysilicon, when the polishing rate monitored by the polishing equipment changes, it can be judged that the polysilicon in the area outside the trench has been polished. However, in order to completely remove the polycrystals in areas other than the trenches, this step can use excessive polishing. When the polishing rate changes, continue polishing for a certain period of time to remove some of the Si ₃ N ₄ layer. In this way, The residue of polysilicon can be completely avoided. Moreover, compared with dry etching, the cost of chemical mechanical polishing is lower, which reduces the process cost of manufacturing trench power devices. See S27' for the implementation effect of this step.

After step S27, the Si ₃ N ₄ transition layer and the SiO ₂ hard mask layer on the Si substrate are removed earlier, and then include forming a P-type body region, forming a source region, forming an insulating dielectric layer, a contact hole, a metal layer and Passivation layer and other steps. It should be pointed out that these steps can be carried out according to the conventional trench-type DMOS preparation method, and since they are the same as those in the prior art, details will not be repeated here.

To sum up, the method for preparing a trench power device provided by the embodiment of the present invention, by changing the process flow, adding a transition layer before trench etching, and subsequently adopting polysilicon polishing method, instead of the current polysilicon dry method Etching solves the polysilicon residue problem caused by the protrusion on the polysilicon surface and the polymer residue in the polysilicon dry etching process, and then solves the gate-source short circuit and leakage problems of the finished product, greatly improving the yield. In addition, compared with dry etching, polishing is used to further reduce the cost.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (5)

1. A method for preparing a trench type power device, characterized in that, comprising: disposing a hard mask layer on the substrate; disposing a transition layer on the hard mask layer; performing photolithography on the transition layer to form a trench window; forming a trench on the substrate in a region corresponding to the trench window; filling the trench with polysilicon; The polysilicon in the area outside the trench is ground away by polishing. 2. The method according to claim 1, wherein the transition layer is a Si ₃ N ₄ layer. 3. The method according to claim 1, wherein the polishing method to grind away the polysilicon in the area outside the trench is specifically: The polysilicon in the area outside the trench is ground away by means of chemical mechanical polishing. 4. The method according to claim 1, wherein the polishing method to grind away the polysilicon in the area outside the trench is specifically: Polishing is used to grind the polysilicon in areas other than the grooves, and when the polishing rate changes, the polishing is stopped. 5. The method according to claim 1, wherein the polishing method to grind away the polysilicon in the area outside the trench is specifically: Grinding the polysilicon in areas other than the trenches by means of polishing; When the polishing rate changes, continue polishing for a certain period of time and then stop polishing.

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