Semiconductor storage device-containing structure and method for manufacturing semiconductor storage device

Abstract

The present invention provides: a semiconductor storage 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 storage device formed on the silicon epitaxial layer; and a method for manufacturing a semiconductor storage device in which the structure is irradiated with a laser to peel and remove the silicon substrate at the oxygen δ-doped layer. Consequently, provided are a semiconductor storage device-containing structure and a method for manufacturing a semiconductor storage device which enables easy thinning.

Description

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

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

[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 recently, and these are revolutionizing the conventional social structure (Non-Patent Document 1).

[0003] Also, 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 with further machine learning and further generative AI is considered to increase more and 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 and HBM (High Bandwidth Memory) are connected by 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).

[0005] Nomura Research Institute Future Creation Center Research Report Vol. 10 "The Future Landscape Transformed by Generative AI What You Should Know About the Suddenly Appeared 'Generative AI'" December 2023 ADMETAPlus2024, Tutorial "Metallization for Memory Devices - Challenging High Bandwidth Memory" Micron Memory Japan, K.K. Naoki Yokoi

[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, several additional methods are considered necessary to thin an entire 300 mm 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 a sag 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 high-cost because it requires the use of an SOI made from two wafers.

[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.

[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 using semiconductor memory.

[0016] As described above, the semiconductor memory device-containing structure of the present invention makes it possible to easily thin the film. This contributes to improving the performance of the HBM (increasing the number of layers). Furthermore, the semiconductor memory device manufacturing method of the present invention makes it possible to manufacture a semiconductor memory device by efficiently and simply thinning the film. This contributes to improving the performance of the HBM (increasing the number of layers).

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

[0018] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0019] As described above, there was a need for a semiconductor memory device-containing structure and a method for manufacturing a semiconductor memory device that could be easily thinned.

[0020] As a result of diligent research into the above-mentioned problems, the present inventors have found that a semiconductor memory-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 makes it possible to easily create a thin film, thereby contributing to the improvement of the performance of HBMs (increase in the number of layers), and have completed the present invention.

[0021] The present inventors have also conducted extensive research on the above-mentioned problems and have found that 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, allows for efficient and simple thinning of the semiconductor memory device, thereby contributing to improved performance of HBMs (increased number of layers), and thus completing the present invention.

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

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

[0024] The silicon substrate 2 is not particularly limited, but for example, its diameter may be 200 to 300 mm, or even larger. It may be doped, its conductivity type may be p-type or n-type, and its resistivity may be low or high. It can be a silicon single crystal substrate manufactured using conventional single crystal manufacturing equipment and procedures (e.g., CZ method or FZ method). Alternatively, an epitaxial wafer obtained by epitaxially growing single crystal silicon on a single crystal silicon wafer may be used.

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

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

[0027] The semiconductor memory device 5 is not particularly limited, but it can be a DRAM that is an 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] (Step to form an oxygen δ-doped 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 formed quickly (for example, within 10 minutes). Through this process, an oxygen δ-doped layer 3 can be formed 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 / cm２ 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 peeling 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 changing the optimal number of layers as needed depending on the laser peeling conditions.

[0034] 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] (Step of forming a silicon epitaxial layer on an oxygen δ-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 step of forming the oxygen δ-doped layer 3.

[0036] In a reduced-pressure CVD apparatus, a silicon epitaxial layer 4 is grown 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 to be formed. As the number of stacked layers of the semiconductor memory device 5 in HBM manufacturing increases, further thinning will progress. Accordingly, the thickness of the silicon epitaxial layer 4 can be adjusted according to the thickness of HBM. The thickness can be controlled by adjusting the growth time.

[0038] (Step of forming a semiconductor memory device on a silicon epitaxial layer) On the substrate fabricated by the procedure as described above, a DRAM serving as HBM is formed as the semiconductor memory device 5.

[0039] (Step of irradiating a silicon substrate with a laser to peel off and remove the silicon substrate with an oxygen δ-doped layer) A laser is irradiated onto the oxygen δ-doped layer 3 from the silicon substrate 2 side. The laser to be irradiated is generally called a CO ２ laser, and a laser that can obtain a large output of around 9 μm wavelength with high efficiency from the vibration level transition of CO ２ molecules by applying an electric discharge to a carbon dioxide gas mixed with helium and nitrogen can be used.

[0040] By irradiating such a laser onto the oxygen δ-doped layer 3, the laser is absorbed by the oxygen δ-doped layer 3, and the stacked oxygen δ-doped layer 3 expands and is peeled off. The higher the number of stacked layers, the higher the absorption rate. Accordingly, the silicon substrate 2 can be peeled off and removed from the semiconductor memory device 5.

[0041] By going through the steps as described above, a self-supporting structure of the semiconductor memory device 5 can be manufactured.

[0042] Hereinafter, the present invention will be specifically described with reference to examples, but this does not limit the present invention.

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

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

[0045] Next, the temperature was raised to 1030°C, and silicon was grown to 2 μm using dichlorosilane as a raw material. As a result, an epitaxial wafer having an oxygen δ-doped layer on a single-crystalline silicon substrate was produced. Using this substrate, a semiconductor memory device (DRAM) was formed in the silicon epitaxial layer.

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

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

[0048] Note that the present invention is not limited to the above-described embodiment. The above-described embodiment is an example, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. A semiconductor memory device-containing structure characterized by comprising 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.

2. A method for manufacturing a semiconductor memory device, comprising the steps of: forming an oxygen delta-doped layer on a silicon substrate; forming a silicon epitaxial layer on the oxygen delta-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 delta-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.

Images