JPWO2020145891A5 - - Google Patents

Description

FIG. 1 shows an example of a typical process for manufacturing photonics chips. Substrate 100 is a process that adds, for example, a Buried Oxide Layer (BOX) layer 102 over the substrate. A waveguide 104 is deposited and a cladding layer 106 is applied. The device is processed to include a plurality of deep trenches 108 (two of which are shown). This is so that the individual chips can be separated from each other at a later stage. After chip processing is complete, a backgrinding process is performed on the wafer (which is placed on an adhesive backing sheet, not shown), resulting in the device shown in FIG. If the thickness requirement is not too thin, the final wafer will have a uniform spread of viable devices. However, thinner devices and other problems associated with backgrinding can damage the entire wafer so that virtually no chips remain after backgrinding. The wafer is thinned directly by mechanical backgrinding. Thickness control and yield are very poor for thin chips.

After the wafer is fabricated and the trenches are formed, the wafer is attached to a film such as Mylar film (not shown) or UV tape. A film is applied to the cladding layer to hold the chip in place during the next stage of the process. Once supported by the film, the wafer undergoes a process that removes the entire substrate. This can include, at least in part, a background grinding process. Using backgrinding, the substrate is reduced from its original thickness to about 50 μm (±25 μm), leaving a total remaining thickness of about 100 μm, to ensure that the backgrinding yield is sufficient. is the minimum thickness of This is because the amount of substrate removed by backgrinding is selected to be optimal to prevent damage to the overlying surface of the wafer. The resulting device is shown in FIG . The backgrinding process involves grinding a portion of the substrate while supporting the wafer on the film using a grinder.

In the next step of the invention, the ground wafer undergoes a silicon wet etch process to remove the remainder to the substrate as shown in FIG . The wet etching process involves exposing the substrate silicon to a solution such as tetramethylammonium hydroxide (TMAH) to remove residual silicon and automatically separate the chips.

As seen in FIG. 2 , the wet etch process removes all material down to the bottom of the deep trench. The buffer layer is made of a non-etchable material and is not etched. The thickness of the buffer layer is predetermined so that the resulting chip has the required thickness. The resulting device therefore has a buffer layer as a support layer, rather than a substrate which normally serves this purpose.

Claims (8)

a buffer layer comprising at least one of SiO ₂ , SiON and SiN and having a predetermined thickness ; and an etch stop layer deposited over the buffer layer;
A semiconductor device having a thickness of less than 50 μm . 2. The semiconductor device according to claim 1, wherein said buffer layer has a thickness of 3 [mu] m to 30 [mu]m. 3. The semiconductor device according to claim 1, wherein said semiconductor device is a photonic chip. A method for manufacturing a plurality of semiconductor devices,
forming a substrate,
forming a buffer layer of at least one of SiO ₂ , SiON and SiN on the substrate and having a predetermined thickness related to the thickness required for the semiconductor device;
forming an etch stop layer on the buffer layer;
forming a plurality of devices on the etch stop layer;
forming at least one layer of cladding material over the device;
forming a plurality of trenches in the layer extending to at least the substrate;
applying a film over the cladding material;
removing at least partially the substrate using an etching process to separate each device from others on the wafer ;
A method of manufacturing a semiconductor device, wherein the thickness of the device is less than 50 μm . 5. The method of claim 4 , further comprising removing the substrate using a combination of back grinding and wet etching processes. 6. A method as claimed in claim 4 or 5 , further comprising isolating the devices by removing a film such that edges of individual devices are defined by the trenches. 7. The method of claim 4 , further comprising forming the trench around each side of the device. 8. The method of claim 4 , further comprising controlling formation of the buffer layer to produce a device with the desired thickness.