Substrate containing carbon-doped silicon epitaxial layer and method for manufacturing same

Abstract

The present invention provides: a substrate containing a carbon-doped silicon epitaxial layer, the substrate having a carbon-doped silicon epitaxial layer on a silicon substrate and a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein the carbon concentration in the carbon-doped silicon epitaxial layer decreases continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side; and a method for manufacturing said substrate. Consequently, a substrate containing a carbon-doped silicon epitaxial layer, in which both good gettering characteristics and a high-quality silicon epitaxial layer having good crystallinity are achieved, and a method for manufacturing said substrate are provided.

Description

Substrate containing carbon-doped silicon epitaxial layer and method for manufacturing same

[0001] The present invention relates to a substrate containing a carbon-doped silicon epitaxial layer and a method for producing the same.

[0002] Solid-state imaging devices, such as CMOS image sensors, can be manufactured using CMOS manufacturing lines, so there is a demand for fast supply to meet demand (Non-Patent Document 1). Recently, there has been a demand for devices with a large number of pixels and high sensitivity. This necessitates substrate gettering.

[0003] This is because the presence of impurities (especially heavy metals) that act as carrier generation centers, particularly in the photodiode portion, can cause white scratches and other defects, but adding gettering capability can suppress these occurrences.

[0004] Regarding gettering, in addition to device process innovations, many studies have been conducted on adding gettering capability to substrates. Examples of such methods include a method of ion-implanting carbon and then growing an epitaxial layer thereon (Patent Document 1), a method of epitaxially growing on a carbon-doped layer (Patent Document 2), a method of doping carbon into an original silicon substrate (Patent Document 3), a method of implanting carbon clusters (Patent Document 4), and further, a method of implanting carbon and As (Patent Document 5), and a method of incorporating silicon atoms, atoms of a group 14 element (C: carbon), and atoms that suppress the diffusion of the atoms of the group 14 element (Patent Document 6).

[0005] Japanese Patent Laid-Open No. 6-338507 Japanese Patent Laid-Open No. 2006-216934 International Publication No. 2008 / 029918 International Publication No. 2012 / 157162 Japanese Patent Laid-Open No. 06-163410 Japanese Patent Laid-Open No. 2009-200231

[0006] Albert J. P. Theuwissen, “There's More to the Picture Than Meets the Eye (and in the future it will only be much more)” Abst. of ISSCC2021, Plenary Session - Invited Papers1-4

[0007] The method of doping carbon during silicon crystal growth in advance is a very effective method because it can be done during crystal growth, but the amount of carbon that can be introduced depends on the solid solubility (thermal equilibrium concentration) during crystal growth, so the introduced carbon concentration cannot be higher than the solid solubility, and carbon cannot be introduced at a high concentration. Therefore, there is a method of introducing carbon by ion implantation, but this requires the use of an ion implantation device, so there is a concern about contamination from the device. Therefore, if carbon could be introduced during epitaxial growth, it would be considered an effective method.

[0008] On the other hand, in conventional ion implantation methods and carbon-doped epitaxial growth, the setting of the carbon concentration is one of the important factors. In particular, in the case of carbon-doped epitaxial growth, it is thought that a high concentration of carbon doping will improve the gettering ability (e.g., due to increased solid solubility caused by strain). However, when growing an epitaxial layer on this carbon-doped layer, there is a concern that the crystallinity of the epitaxial layer will be deteriorated due to strain caused by the high concentration of carbon doping.

[0009] Therefore, it is required to improve the crystallinity of the silicon epitaxial layer formed on the carbon-doped silicon epitaxial layer while having a high gettering ability.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a substrate containing a carbon-doped silicon epitaxial layer that combines good gettering characteristics with a high-quality silicon epitaxial layer having good crystallinity, and a method for manufacturing the same.

[0011] The present invention has been made to achieve the above-mentioned object, and provides a carbon-doped silicon epitaxial layer-containing substrate having a carbon-doped silicon epitaxial layer on a silicon substrate and a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, in which the carbon concentration of the carbon-doped silicon epitaxial layer decreases continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side.

[0012] Such a carbon-doped silicon epitaxial layer-containing substrate provides both excellent gettering properties and a high-quality silicon epitaxial layer with good crystallinity.

[0013] At this time, the carbon concentration on the silicon substrate side of the carbon-doped silicon epitaxial layer is 4×10 ２１ atoms / cm ３ It can be the following:

[0014] This makes it possible to effectively suppress distortion caused by high-concentration carbon doping.

[0015] At this time, the carbon concentration on the silicon substrate side of the carbon-doped silicon epitaxial layer is 1×10 １９ atoms / cm ３ It can be assumed that the above is the case.

[0016] This gives the carbon-doped silicon epitaxial layer better gettering properties.

[0017] At this time, the carbon concentration on the non-carbon-doped silicon epitaxial layer side of the carbon-doped silicon epitaxial layer is 1×10 １９ atoms / cm ３ It can be the following:

[0018] This results in a non-carbon-doped silicon epitaxial layer of higher quality and better crystallinity.

[0019] The present invention has also been made to achieve the above-mentioned object, and provides a method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate, comprising the steps of forming a carbon-doped silicon epitaxial layer on a silicon substrate and forming a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein, in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer is decreased continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side.

[0020] According to such a method for manufacturing a substrate containing a carbon-doped silicon epitaxial layer, it is possible to manufacture a substrate containing a carbon-doped silicon epitaxial layer that has both good gettering properties and a high-quality silicon epitaxial layer with good crystallinity.

[0021] At this time, in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the silicon substrate side of the carbon-doped silicon epitaxial layer is set to 4×10 ２１ atoms / cm ３ It can be as follows:

[0022] This makes it possible to effectively suppress distortion caused by high-concentration carbon doping.

[0023] At this time, in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is set to 1×10 １９ atoms / cm ３ It can be more than that.

[0024] This allows the formation of a carbon-doped silicon epitaxial layer with better gettering properties.

[0025] At this time, in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration on the non-carbon-doped silicon epitaxial layer side of the carbon-doped silicon epitaxial layer is set to 1×10 １９ atoms / cm ３ It can be as follows:

[0026] This makes it possible to form a high-quality non-carbon-doped silicon epitaxial layer with better crystallinity.

[0027] As described above, the carbon-doped silicon epitaxial layer-containing substrate of the present invention achieves both excellent gettering properties and a high-quality silicon epitaxial layer with good crystallinity. Furthermore, the method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate of the present invention makes it possible to manufacture a carbon-doped silicon epitaxial layer-containing substrate that achieves both excellent gettering properties and a high-quality silicon epitaxial layer with good crystallinity.

[0028] 1 is a schematic diagram of a carbon-doped silicon epitaxial layer-containing substrate according to an embodiment of the present invention; 2 is a graph showing the relationship between the amount of carbon doping in a carbon-doped silicon epitaxial layer and the lattice spacing of silicon; 3 is a graph showing the results of measuring the carbon concentration of a carbon-doped silicon epitaxial layer-containing substrate according to an example by SIMS; and 4 is a graph showing the results of SIMS analysis of metal gettered by carbon when a carbon-doped silicon epitaxial layer-containing substrate according to an example is intentionally contaminated.

[0029] The present invention will be described in detail below, but the present invention is not limited thereto.

[0030] As described above, there has been a demand for a substrate containing a carbon-doped silicon epitaxial layer that combines good gettering properties with a high-quality silicon epitaxial layer having good crystallinity, and a method for manufacturing the same.

[0031] As a result of extensive research into the above-mentioned problems, the present inventors have found that a carbon-doped silicon epitaxial layer-containing substrate having a carbon-doped silicon epitaxial layer on a silicon substrate and a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, in which the carbon concentration of the carbon-doped silicon epitaxial layer decreases continuously or stepwise from the silicon substrate side to the non-carbon-doped silicon epitaxial layer side, can provide a high-quality silicon epitaxial layer with both good gettering properties and good crystallinity, and have completed the present invention.

[0032] As a result of intensive research into the above-mentioned problems, the present inventors have found that a carbon-doped silicon epitaxial layer-containing substrate can be produced that has both excellent gettering properties and a high-quality silicon epitaxial layer with good crystallinity, by using a method for producing a carbon-doped silicon epitaxial layer-containing substrate, the method comprising the steps of forming a carbon-doped silicon epitaxial layer on a silicon substrate and forming a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein, in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer is reduced continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side, and have completed the present invention.

[0033] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0034] [Carbon-doped silicon epitaxial layer-containing substrate] A schematic diagram of a carbon-doped silicon epitaxial layer-containing substrate according to an embodiment of the present invention is shown in Figure 1. As shown in Figure 1, the carbon-doped silicon epitaxial layer-containing substrate 1 according to the present invention is a carbon-doped silicon epitaxial layer-containing substrate having a carbon-doped silicon epitaxial layer 3 on a silicon substrate 2 and a non-carbon-doped silicon epitaxial layer 4 on the carbon-doped silicon epitaxial layer 3.

[0035] The silicon substrate 2 is not particularly limited, but may have a diameter of 150 mm or more, may be of either p-type or n-type conductivity, and may have a low resistivity of 0.1 Ω cm or less or a high resistivity of 1000 Ω cm or more. The silicon substrate may be a silicon single crystal substrate manufactured using conventional single crystal manufacturing equipment and procedures.

[0036] The carbon-doped silicon epitaxial layer 3 has a carbon concentration that decreases continuously or stepwise from the silicon substrate 2 side toward the non-carbon-doped silicon epitaxial layer 4 side.

[0037] Such a gradient in carbon concentration allows gettering to occur at the interface between the non-carbon-doped silicon epitaxial layer 4, which is the active layer, and the silicon substrate 2, which is far from the interface, thereby suppressing diffusion current and providing good gettering characteristics. In addition, the non-carbon-doped silicon epitaxial layer 4 becomes a high-quality silicon epitaxial layer with good crystallinity.

[0038] The carbon concentration on the silicon substrate 2 side is 4×10 ２１ atoms / cm ３ It is preferable that the carbon content is equal to or less than 1000 .mu.m. This makes it possible to effectively suppress distortion caused by high concentration carbon doping.

[0039] The carbon concentration on the silicon substrate 2 side is 1×10 １９ atoms / cm ３ This makes it possible for the carbon-doped silicon epitaxial layer 3 to have better gettering properties.

[0040] 2 is a graph showing the relationship between the carbon doping amount and the silicon lattice spacing in a carbon-doped silicon epitaxial layer. １９ atoms / cm ３ For at least this reason, the carbon concentration on the non-carbon-doped silicon epitaxial layer 4 side is 1×10 １９ atoms / cm ３ The lower limit is not particularly limited, but is, for example, 0 atoms / cm３ This allows the non-carbon-doped silicon epitaxial layer 4 to have better crystallinity and higher quality.

[0041] The thickness of the carbon-doped silicon epitaxial layer 3 is not particularly limited and can be changed as appropriate.

[0042] The non-carbon-doped silicon epitaxial layer 4 is not particularly limited, and may be formed by a conventional epitaxial growth process.

[0043] [Method for Manufacturing a Carbon-Doped Silicon Epitaxial Layer-Containing Substrate] Next, a method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate according to the present invention will be described with reference to Figures 1 and 2. The method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate 1 according to the present invention is a method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate including the steps of forming a carbon-doped silicon epitaxial layer 3 on a silicon substrate 2 and forming a non-carbon-doped silicon epitaxial layer 4 on the carbon-doped silicon epitaxial layer 3.

[0044] (Step of forming a carbon-doped silicon epitaxial layer) A carbon-doped Si layer is epitaxially grown on a silicon substrate 2 under reduced pressure in a low-pressure CVD apparatus using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material.

[0045] During epitaxial growth, the carbon concentration of the carbon-doped silicon epitaxial layer 3 is decreased continuously or stepwise from the silicon substrate 2 side toward the non-carbon-doped silicon epitaxial layer 4 side.

[0046] By providing such a gradient in carbon concentration, gettering occurs at the interface with the silicon substrate 2, which is far from the non-carbon-doped silicon epitaxial layer 4, which is the active layer, and therefore diffusion current can be suppressed, making it possible to form a carbon-doped silicon epitaxial layer 3 with good gettering properties. In addition, a high-quality non-carbon-doped silicon epitaxial layer 4 with good crystallinity can be formed on the carbon-doped silicon epitaxial layer 3.

[0047] At this time, the growth temperature is preferably in the range of 700°C to 900°C, more preferably in the range of 730°C to 750°C, so that the carbon-doped silicon epitaxial layer 3 with fewer defects can be formed.

[0048] The pressure inside the furnace during growth is not particularly limited, and can be set to, for example, 1 to 100 Torr.

[0049] At this time, the carbon concentration of the carbon-doped silicon epitaxial layer 3 on the silicon substrate 2 side is set to 4×10 ２１ atoms / cm ３ It is preferable that the carbon content be set to the following: This makes it possible to effectively suppress distortion caused by high-concentration carbon doping.

[0050] The carbon concentration of the carbon-doped silicon epitaxial layer 3 on the silicon substrate 2 side is set to 1×10 １９ atoms / cm ３ This makes it possible to form a carbon-doped silicon epitaxial layer 3 having better gettering properties.

[0051] Thereafter, the flow rate of trimethylsilane, monomethylsilane, or other carbon source gas is reduced to decrease the carbon concentration. There are two main ways to change the carbon concentration: one is to continuously change the flow rate of trimethylsilane, monomethylsilane, or other carbon source gas to continuously change the concentration, and the other is to fix the flow rate at a predetermined value for a certain period of time and then change the flow rate stepwise. The method can be determined taking into account the accuracy of the growth apparatus, etc.

[0052] At this time, the carbon concentration on the non-carbon-doped silicon epitaxial layer 4 side is set to 1×10 where no change in the lattice spacing is observed even when carbon is doped, as shown in FIG. １９ atoms / cm ３ The lower limit is not particularly limited, but for example, ３ This allows the formation of a high-quality non-carbon-doped silicon epitaxial layer 4 with better crystallinity.

[0053] The thickness of the carbon-doped silicon epitaxial layer 3 is not particularly limited and can be changed as appropriate.

[0054] (Step of forming non-carbon-doped silicon epitaxial layer) Subsequently, a non-carbon-doped silicon epitaxial layer 4 is formed on the carbon-doped silicon epitaxial layer 3. The growth conditions for the non-carbon-doped silicon epitaxial layer 4 are not particularly limited, and the layer can be formed by a conventional epitaxial growth process.

[0055] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0056] A boron-doped single crystal silicon substrate having a diameter of 300 mm, a plane orientation of (100), and a resistivity of 10 Ω·cm was prepared.

[0057] On a silicon substrate, a low-pressure CVD apparatus was used, and trimethylsilane was used as a source gas. The growth temperature was 700°C, the furnace pressure was 10 Torr, and carbon was deposited at 1×10 ２０ atoms / cm ３ A doped Si epitaxial layer was grown to a thickness of 50 nm.

[0058] After that, by the same method, 1 × 10 １９ atoms / cm ３ A carbon-doped Si epitaxial layer was grown to a thickness of 500 nm.

[0059] Next, SiH ４ The gas was used as a source gas, and epitaxial growth was performed for 60 minutes at a flow rate of 1000 sccm, a growth temperature of 1080° C., and a furnace pressure of 10 Torr to grow a Si layer (non-carbon-doped silicon epitaxial layer) to a thickness of 1.5 μm, thereby producing a substrate containing a carbon-doped silicon epitaxial layer.

[0060] The carbon concentration profile of the obtained carbon-doped silicon epitaxial layer-containing substrate was evaluated using a SIMS7f manufactured by Cameca Co., Ltd. The evaluation results are shown in FIG.

[0061] As shown in FIG. 3, it can be seen that the carbon concentration decreases stepwise from the interface between the silicon substrate and the carbon-doped silicon epitaxial layer to the non-carbon-doped silicon epitaxial layer.

[0062] The carbon-doped silicon epitaxial layer-containing substrate thus obtained was doped with a surface concentration of 1×10 １２ atoms / cm ２ The specimens were intentionally contaminated with a nitric acid solution of Ni and Cu at a concentration of 1000 ppm, and then subjected to a diffusion treatment at 650°C for 15 minutes in a horizontal furnace. The metal concentration profile was then evaluated using a SIMS7f manufactured by Cameca Corporation. The evaluation results are shown in Figure 4.

[0063] As a result, as shown in FIG. 4, it was found that Ni and Cu were gettered to the interface (high carbon concentration layer) between the silicon substrate and the carbon-doped silicon epitaxial layer.

[0064] Furthermore, XRD measurement of the non-carbon-doped silicon epitaxial layer revealed that it was a single-crystal silicon epitaxial layer of high quality.

[0065] As described above, according to the examples of the present invention, it was possible to manufacture a substrate containing a carbon-doped silicon epitaxial layer that had both good gettering properties and a high-quality silicon epitaxial layer with good crystallinity.

[0066] This specification includes the following aspects: [1]: A carbon-doped silicon epitaxial layer-containing substrate having a carbon-doped silicon epitaxial layer on a silicon substrate and a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein the carbon concentration of the carbon-doped silicon epitaxial layer decreases continuously or stepwise from the silicon substrate side to the non-carbon-doped silicon epitaxial layer side; [2]: A carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is 4×10 ２１ atoms / cm ３The carbon-doped silicon epitaxial layer-containing substrate according to the above item [1], wherein the carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is 1×10 １９ atoms / cm ３ [4]: The carbon concentration of the carbon-doped silicon epitaxial layer on the non-carbon-doped silicon epitaxial layer side of the carbon-doped silicon epitaxial layer is 1×10 or more. １９ atoms / cm ３ The carbon-doped silicon epitaxial layer-containing substrate according to [1], [2], or [3], comprising the following: [5]: A method for manufacturing a carbon-doped silicon epitaxial layer-containing substrate, comprising the steps of forming a carbon-doped silicon epitaxial layer on a silicon substrate and forming a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer is decreased continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side. [6]: In the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is decreased to 4×10 ２１ atoms / cm ３ [7]: in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is set to 1×10 １９ atoms / cm ３ [8]: In the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer on the side of the non-carbon-doped silicon epitaxial layer is set to 1×10 or more. １９ atoms / cm ３A method for producing a carbon-doped silicon epitaxial layer-containing substrate according to [5], [6] or [7] above, which comprises:

[0067] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A carbon-doped silicon epitaxial layer-containing substrate having a carbon-doped silicon epitaxial layer on a silicon substrate and a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein the carbon concentration of the carbon-doped silicon epitaxial layer decreases continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side.

2. The carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is 4×10 ２１ atoms / cm ３ 2. The carbon-doped silicon epitaxial layer-containing substrate of claim 1, wherein:

3. The carbon concentration of the carbon-doped silicon epitaxial layer on the silicon substrate side is 1×10 １９ atoms / cm ３ 2. The carbon-doped silicon epitaxial layer-containing substrate according to claim 1, wherein the carbon-doped silicon epitaxial layer-containing substrate is a silicon epitaxial layer.

4. The carbon concentration on the non-carbon-doped silicon epitaxial layer side of the carbon-doped silicon epitaxial layer is 1×10 １９ atoms / cm ３ 4. The substrate containing a carbon-doped silicon epitaxial layer according to claim 1, wherein:

5. A method for producing a substrate containing a carbon-doped silicon epitaxial layer, comprising the steps of forming a carbon-doped silicon epitaxial layer on a silicon substrate and forming a non-carbon-doped silicon epitaxial layer on the carbon-doped silicon epitaxial layer, wherein in the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration of the carbon-doped silicon epitaxial layer is decreased continuously or stepwise from the silicon substrate side toward the non-carbon-doped silicon epitaxial layer side.

6. In the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration on the silicon substrate side of the carbon-doped silicon epitaxial layer is set to 4×10 ２１ atoms / cm ３ 6. The method for producing a substrate containing a carbon-doped silicon epitaxial layer according to claim 5, wherein:

7. In the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration on the silicon substrate side of the carbon-doped silicon epitaxial layer is set to 1×10 １９ atoms / cm ３ 6. The method for producing a substrate containing a carbon-doped silicon epitaxial layer according to claim 5, wherein the method comprises the steps of:

8. In the step of forming the carbon-doped silicon epitaxial layer, the carbon concentration on the non-carbon-doped silicon epitaxial layer side of the carbon-doped silicon epitaxial layer is set to 1×10 １９ atoms / cm ３ 8. The method for producing a substrate containing a carbon-doped silicon epitaxial layer according to claim 5, wherein:

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