Semiconductor memory device-containing structure and method for manufacturing a semiconductor memory device

Abstract

The objective is to provide a semiconductor memory device-containing structure that can be easily thinned and a method for manufacturing a semiconductor memory device. [Solution] A semiconductor memory device-containing structure having a silicon substrate, an oxygen δ-doped layer on the silicon substrate, a silicon epitaxial layer on the oxygen δ-doped layer, and a semiconductor memory device formed on the silicon epitaxial layer; and a method for manufacturing a semiconductor memory device, comprising irradiating the structure with a laser to peel off and remove the silicon substrate from the oxygen δ-doped layer.

Description

Technical Field

[0001] The present invention relates to a semiconductor memory device-containing structure and a method for manufacturing a semiconductor memory device.

Background Art

[0002] In the 2000s, the demand for AI servers that can machine-learn a large number of data on a server and dramatically improve the accuracy of image recognition has exploded. Furthermore, in recent years, a technology called generative AI, which generates data based on machine-learned data, has become mainstream. Conventionally, it has been possible to output search results based on the results of machine learning, but generative AI, which will attract attention in the future, outputs new results. As an example of this, there is a case where a large number of patents have been filed by SoftBank Group Corporation in a short period of time, and these are revolutionizing the conventional social structure (Non-Patent Document 1).

[0003] In addition, in machine learning and generative AI, since it is considered that the content of the data to be learned will naturally differ, the demand for AI servers that replace conventional general-purpose servers for machine learning and generative AI is expected to increase even more in the future (the era of artificial intelligence).

[0004] The GPU (Graphics Processing Unit) used in AI servers has a structure in which the main core of the processor is connected to HBM (High Bandwidth Memory) via a silicon interposer. As a heat countermeasure, a heat sink is installed on the processor and HBM. For this reason, the height of the HBM must be the same as that of the processor (Non-Patent Document 2). [[ID=))]]

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] HBMs have a stacked structure of DRAMs, and to improve performance, the number of stacks needs to be increased. However, due to the height constraints mentioned above, the height of individual DRAMs needs to be reduced (thinner). As described in Non-Patent Literature 2, it is expected that they will become even thinner with each generation, so the challenge will be how to make them thinner.

[0007] While grinding and CMP are certainly methods for thinning substrates, several additional methods are considered necessary to thin an entire 300mm diameter substrate. One such method is the etch-stop method using dopant concentration differences. This method involves depositing layers with different concentrations and utilizing the resulting difference in etching rate due to the difference in resistance. However, if there is sagging in the dopant profile, it becomes difficult to obtain the desired etching rate difference.

[0008] Another method involves using an SOI substrate. This technique involves forming elements on an SOI layer and then thinning them using a BOX film, which is an oxide film. While this is a reliable method, it has the drawback of being costly because it requires the use of two wafers for the SOI.

[0009] The present invention has been made to solve the above problems, and aims to provide a semiconductor memory device-containing structure that can be easily thinned and a method for manufacturing a semiconductor memory device. [Means for solving the problem]

[0010] The present invention has been made to achieve the above objective and provides a semiconductor memory device-containing structure having a silicon substrate, an oxygen δ-doped layer on the silicon substrate, a silicon epitaxial layer on the oxygen δ-doped layer, and a semiconductor memory device formed on the silicon epitaxial layer.

[0011] Such a semiconductor memory-containing structure makes it possible to easily create thin films.

[0012] The present invention also provides a method for manufacturing a semiconductor memory device, comprising the steps of: forming an oxygen δ-doped layer on a silicon substrate; forming a silicon epitaxial layer on the oxygen δ-doped layer; forming a semiconductor memory device on the silicon epitaxial layer; and irradiating the silicon substrate with a laser to peel off and remove the silicon substrate from the oxygen δ-doped layer.

[0013] According to this method of manufacturing semiconductor memory devices, it is possible to manufacture semiconductor memory devices by efficiently and simply thinning the film.

[0014] In this process, the thickness of the silicon epitaxial layer can be adjusted according to the thickness of the semiconductor memory device during the process of forming the silicon epitaxial layer.

[0015] This allows the thickness of the silicon epitaxial layer to be adjusted according to the thickness of the HBM used in the semiconductor memory device. [Effects of the Invention]

[0016] As described above, according to the semiconductor memory device-containing structure of the present invention, thinning can be easily performed. This contributes to the high performance (increase in the number of stacked layers) of HBM. Also, according to the method for manufacturing a semiconductor memory device of the present invention, it is possible to efficiently and simply perform thinning to manufacture a semiconductor memory device. This can contribute to the high performance (increase in the number of stacked layers) of HBM.

Brief Description of the Drawings

[0017] [Figure 1] A schematic cross-sectional view of an example of the semiconductor memory device-containing structure of the present invention is shown.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0019] As described above, there has been a demand for a semiconductor memory device-containing structure and a method for manufacturing a semiconductor memory device that can easily perform thinning.

[0020] As a result of intensive studies on the above problems, the present inventors have found that a semiconductor memory device-containing structure having a silicon substrate, a δ-doped layer of oxygen on the silicon substrate, a silicon epitaxial layer on the δ-doped layer of oxygen, and a semiconductor memory device formed on the silicon epitaxial layer can easily perform thinning, and thereby contributes to the high performance (increase in the number of stacked layers) of HBM, and completed the present invention.

[0021] As a result of intensive studies on the above problems, the present inventors have found that a method for manufacturing a semiconductor memory device including a step of forming a δ-doped layer of oxygen on a silicon substrate, a step of forming a silicon epitaxial layer on the δ-doped layer of oxygen, a step of forming a semiconductor memory device in the silicon epitaxial layer, and a step of irradiating the silicon substrate with a laser to peel off and remove the silicon substrate with the δ-doped layer of oxygen can efficiently and simply thin the semiconductor memory device, thereby making it possible to contribute to the improvement of the performance (increase in the number of stacked layers) of HBM, and completed the present invention.

[0022] In the present invention, doping at a high concentration with a thickness of several atomic layers is referred to as "delta doping" (also referred to as "δ doping"), and a layer formed by delta doping is referred to as a "δ-doped layer". For example, when the doping element is oxygen, it is referred to as "δ doping of oxygen" or "δ-doped layer of oxygen".

[0023] [Semiconductor memory device-containing structure] Hereinafter, the semiconductor memory device-containing structure of the present invention will be described with reference to FIG. 1. As shown in FIG. 1, a semiconductor memory device-containing structure 1 which is an example of an embodiment of the present invention includes a silicon substrate 2, a δ-doped layer 3 of oxygen on the silicon substrate 2, a silicon epitaxial layer 4 on the δ-doped layer 3 of oxygen, and a semiconductor memory device 5 formed in the silicon epitaxial layer 4.

[0024] The silicon substrate 2 is not particularly limited. For example, the diameter may be 200 to 300 mm, or even more. It may be doped, and the conductivity type may be p-type or n-type, and may have a low resistivity or a high resistivity. It can be a silicon single crystal substrate manufactured by the same single crystal manufacturing apparatus and procedure as in the prior art (for example, CZ method or FZ method). Further, an epitaxial wafer obtained by epitaxially growing single crystal silicon on a single crystal silicon wafer may also be used.

[0025] The thickness and concentration of the δ-doped layer 3 of oxygen will be described in detail in the method for manufacturing a semiconductor memory device described later.

[0026] In another embodiment, the structure may consist of multiple alternating layers of oxygen-delta-doped layers 3 and silicon epitaxial layers 4 stacked on a silicon substrate 2.

[0027] The semiconductor memory device 5 is not particularly limited, but it can be a DRAM made of HBM.

[0028] [Method for manufacturing a semiconductor memory device] Next, the method for manufacturing a semiconductor memory device of the present invention will be described with reference to Figure 1. The method for manufacturing a semiconductor memory device of the present invention includes the steps of forming an oxygen δ-doped layer 3 on a silicon substrate 2, forming a silicon epitaxial layer 4 on the oxygen δ-doped layer 3, forming a semiconductor memory device 5 on the silicon epitaxial layer 4, and irradiating the silicon substrate 2 with a laser to peel off and remove the silicon substrate 2 from the oxygen δ-doped layer 3.

[0029] (Process of forming an oxygen-doped δ layer on a silicon substrate) A silicon substrate 2 is prepared and treated with an oxidizing chemical solution, after which a silicon epitaxial layer is rapidly formed (for example, within 10 minutes). This process allows for the formation of an oxygen δ-doped layer 3 between the silicon substrate 2 and the silicon epitaxial layer.

[0030] In the oxygen δ-doped layer 3, oxygen atoms are stable at the bond center position between silicon atoms and the nearest silicon atom. Therefore, assuming the presence of one atomic layer of oxygen, the planar concentration of oxygen is 1.36 × 10⁻¹⁶. 15 atoms / cm 2 Therefore, the planar concentration of oxygen is 1.0 × 10⁻⁶. 15 atoms / cm 2 In this case, it corresponds to 0.74 atomic layers.

[0031] The concentration of the oxygen δ-doped layer 3 can be controlled by adjusting the temperature, concentration, and processing time of the oxidizing chemical solution used to treat the silicon substrate 2.

[0032] The thickness of the oxygen δ-doped layer 3 is preferably 3 nm or less, and more preferably 1 nm or less. A thicker layer is advantageous in subsequent laser irradiation delamination processes, but within this thickness range, polycrystallization of the epitaxial layer formed on the oxygen δ-doped layer 3 can be effectively prevented.

[0033] The oxygen δ-doped layer 3 and the silicon epitaxial layer 4 on top of it can be made into thin films, and multiple layers of these can be stacked. This allows for the optimal number of layers to be changed as needed depending on the laser peeling conditions.

[0034] Alternatively, before forming the oxygen δ-doped layer 3, the silicon substrate 2 may be subjected to DHF cleaning or hydrogen baking to remove the native oxide film on the surface of the silicon substrate 2.

[0035] (A process of forming a silicon epitaxial layer on an oxygen-delta doped layer) A silicon epitaxial layer 4 is formed on the oxygen δ-doped layer 3. At this time, epitaxial growth can be continued in the same reduced-pressure CVD apparatus used in the process of forming the oxygen δ-doped layer 3.

[0036] In a vacuum CVD apparatus, a silicon epitaxial layer 4 is grown under reduced pressure using monosilane gas or dichlorosilane gas as a raw material. The silicon epitaxial layer 4 can be formed at temperatures ranging from approximately 700°C to 1000°C.

[0037] The thickness of the silicon epitaxial layer 4 can be adjusted according to the thickness of the semiconductor memory device 5 being formed. As the number of stacked semiconductor memory devices 5 in HBM manufacturing increases, the thinning process progresses further, which allows the thickness of the silicon epitaxial layer 4 to be adjusted according to the thickness of the HBM. The thickness can be controlled by adjusting the growth time.

[0038] (Process of forming a semiconductor memory device on a silicon epitaxial layer) On the substrate fabricated using the procedure described above, a DRAM, which will be HBM, is formed as the semiconductor memory device 5.

[0039] (A process in which a silicon substrate is irradiated with a laser, and the silicon substrate is peeled off and removed by the oxygen delta-doped layer.) A laser is irradiated onto the oxygen δ-doped layer 3 from the silicon substrate 2 side. The laser used for irradiation is generally called a CO2 laser, and it is possible to use one that can obtain a large output with a wavelength of around 9 μm with high efficiency by applying an electrical discharge to carbon dioxide gas (a mixture of helium and nitrogen) to induce vibrational level transitions in CO2 molecules.

[0040] When such a laser is irradiated onto the oxygen delta-doped layer 3, the laser is absorbed by the oxygen delta-doped layer 3, causing the stacked oxygen delta-doped layers 3 to expand and be peeled off. The absorption rate increases with the number of layers. This allows the silicon substrate 2 to be peeled off and removed from the semiconductor memory device 5.

[0041] By following the process described above, the self-contained structure of the semiconductor memory device 5 can be manufactured. [Examples]

[0042] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention.

[0043] A single-crystal silicon substrate with a diameter of 300 mm, a crystal orientation of (100), boron doping, and a resistivity of 10 Ω·cm was prepared.

[0044] After SC1 cleaning was performed on a single-crystal silicon substrate, a 50 nm Si layer was rapidly grown in a reduced-pressure CVD apparatus at 700°C and 10 Torr using monosilane as the raw material gas.

[0045] Next, the temperature was raised to 1030°C, and silicon was grown to a thickness of 2 μm using dichlorosilane as the raw material. This resulted in the fabrication of an epitaxial wafer with an oxygen delta-doped layer on a single-crystal silicon substrate. A semiconductor memory device (DRAM) was then formed on the silicon epitaxial layer using this substrate.

[0046] Next, a resin plate was bonded to this surface as a retaining agent, and an infrared laser with a wavelength of 9 μm was irradiated from the back side (single-crystal silicon substrate side) to peel off the single-crystal silicon substrate at the oxygen δ-doped layer, thereby manufacturing a semiconductor memory device (DRAM) that was thinned to 2 μm for HBM.

[0047] As described above, according to the embodiments of the present invention, it was possible to easily thin the film and manufacture a semiconductor memory device that contributes to improving the performance of HBM (increasing the number of layers).

[0048] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0049] 1... Semiconductor memory device-containing structure, 2... Silicon substrate, 3... Oxygen δ-doped layer 4…Silicon epitaxial layer, 5…Semiconductor memory device.

Claims

1. A silicon substrate and The oxygen δ-doped layer on the silicon substrate, A silicon epitaxial layer on the oxygen δ-doped layer, A semiconductor memory device-containing structure characterized by having a semiconductor memory device formed on the silicon epitaxial layer.

2. A process of forming an oxygen δ-doped layer on a silicon substrate, A step of forming a silicon epitaxial layer on the oxygen δ-doped layer, The process of forming a semiconductor memory device on the silicon epitaxial layer, A method for manufacturing a semiconductor memory device, characterized by including the step of irradiating the silicon substrate with a laser to peel off and remove the silicon substrate with the oxygen δ-doped layer.

3. The method for manufacturing a semiconductor memory device according to claim 2, characterized in that, in the step of forming the silicon epitaxial layer, the thickness of the silicon epitaxial layer is adjusted according to the thickness of the semiconductor memory device.

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