Disclosure of Invention
The invention mainly aims to provide a manufacturing method of compressive stress GOI, which utilizes a channel to effectively inhibit interface defects caused by germanium Ge crystal lattice surface defects, repeats a channel forming and selective Ge epitaxial method and can also minimize the Ge defect density.
In order to achieve the above object, the present invention provides the following technical solutions.
A manufacturing method of compressive stress GOI comprises the following steps:
step a: forming a silicon oxide layer on a first substrate, then carrying out patterned etching on the silicon oxide layer to form a plurality of channels, wherein the channels penetrate through the silicon oxide layer;
step b: selectively and epitaxially growing a second germanium layer on the surface of the patterned silicon oxide layer, and then carrying out chemical mechanical polishing;
step c: repeating the steps a to b for zero times or at least one time, then bonding with a second substrate by taking the final germanium layer as a bonding interface, etching until only the second substrate and the final germanium layer are remained, and flattening; the second substrate is a silicon wafer deposited with a buried oxide layer, and the buried oxide layer is used as a bonding interface during bonding;
if the steps a to b are repeated zero times in the step c, before the step a of forming the silicon oxide layer, the method further comprises: a first layer of germanium is first deposited on a first substrate and chemically mechanically polished until the first layer of germanium is in a relaxed state.
Compared with the prior art, the invention achieves the following technical effects:
(1) the silicon oxide is used for forming a channel, and the channel can effectively inhibit interface defects caused by germanium Ge crystal lattice surface defects, so that a compressive stress type GOI structure is obtained, and the yield of devices is improved;
(2) repeating the channel formation and selective epitaxy of Ge multiple times may also minimize the defect density of Ge.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
Various structural schematics according to embodiments of the present disclosure are shown in the figures. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers, and relative sizes and positional relationships therebetween shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, as actually required.
In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, it can be directly on the other layer/element or intervening layers/elements may be present. In addition, if a layer/element is "on" another layer/element in one orientation, then that layer/element may be "under" the other layer/element when the orientation is reversed.
The invention inhibits interface defects caused by germanium Ge crystal lattice surface defects by Selectively Epitaxially Growing (SEG) germanium on a channel, and the specific process is as follows:
step a: forming a silicon oxide layer on a first substrate, then carrying out patterned etching on the silicon oxide layer to form a plurality of channels, wherein the channels penetrate through the silicon oxide layer;
step b: selectively and epitaxially growing a second germanium layer on the surface of the patterned silicon oxide layer, and then carrying out chemical mechanical polishing;
step c: repeating the steps a to b for zero times or at least one time, then bonding with a second substrate by taking the final germanium layer as a bonding interface, etching until only the second substrate and the final germanium layer are remained, and flattening; the second substrate is a silicon wafer with a front surface deposited with a buried oxide layer, and the buried oxide layer is used as a bonding interface during bonding;
if the steps a to b are repeated zero times in the step c, before the step a of forming the silicon oxide layer, the method further comprises: a first layer of germanium is first deposited on a first substrate and chemically mechanically polished until the first layer of germanium is in a relaxed state.
In the above method, the first substrate may be any substrate known to those skilled in the art for supporting semiconductor integrated circuit components, such as silicon-on-insulator (SOI), silicon wafer, germanium, silicon-germanium, gallium arsenide, or germanium-on-insulator; since the first substrate is used as a sacrificial layer, a silicon wafer having high cost performance is preferably selected.
The silicon oxide layer to be patterned may be formed by a thermal oxidation (dry or wet oxygen) process, chemical vapor deposition, atomic layer deposition, or the like.
The patterning etching means of the silicon oxide layer may be dry method, wet method or plasma, etc., and is performed in combination with a photoresist mask, and the plurality of trenches are preferably arranged regularly, for example, symmetrically at equal intervals, etc. The width between the channels is adjusted as desired.
The goal of chemical mechanical polishing is primarily to bring the germanium layer to a relaxed state, typically within 9 seconds.
The buried oxide layer in the second substrate is silicon oxide SiO2Etc. insulating material.
The number of times said steps a to b are repeated in step c is generally determined according to the following principle: repeating until the defect density of the last germanium layer is no longer reduced. In the process of repeating the steps a to b, the channel formed in the step a and the channel formed in the previous step a are arranged in a staggered mode, so that the defect in the channel can be prevented from extending to the bottom of the upper epitaxial layer, and the quality of the upper germanium film can be greatly improved.
In addition, the addition of the first germanium layer is more beneficial to inhibiting interface defects caused by surface defects of germanium Ge crystal lattices. The first germanium layer may be formed by any means including, but not limited to, typical global epitaxy and selective epitaxy.
One embodiment of the present invention is as follows.
Example 1
The process flow of the morphology change shown in fig. 1 to 6 is as follows:
in a first step, a first germanium layer 102 is deposited on a silicon wafer 101 and then CMP is performed until it is in a relaxed state, as shown in the topography of fig. 1.
Secondly, a silicon oxide layer 103 is deposited by PECVD means, as shown in the figure 2.
Third, the silicon oxide layer is patterned to form a plurality of trenches 104, as shown in fig. 3.
Fourth, second germanium layer 105 is selectively epitaxially grown on the patterned silicon oxide layer surface, followed by CMP, as shown in the topography of fig. 4.
And fifthly, selecting another silicon wafer with a silicon oxide layer on the surface as a second substrate 106, bonding the silicon oxide layer with the semiconductor structure formed in the previous step by using the silicon oxide layer as a bonding interface, and taking the second germanium layer of the semiconductor structure in the fourth step as a bonding interface, wherein the shape is shown in fig. 5.
Sixthly, etching to remove the sacrificial layer: etching to leave only the second substrate and the final germanium layer, and planarizing to obtain the GOI structure, such as the topography shown in fig. 6.
It is also possible to repeat the second through fourth steps one or more times before the fifth bonding step until the defect density of the final germanium layer is no longer reduced, and the invention also includes these embodiments with a preferred staggered arrangement between the channels of adjacent layers. For example, when the process is repeated 1 time, the profile shown in fig. 7 is formed, and then the sacrificial layer is bonded to the second substrate and removed.
Another embodiment of the present invention is as follows.
Example 2
The process flow for the profile variation shown in fig. 8 to 15 is as follows:
in the first step, a silicon oxide layer 202 is deposited on a silicon wafer 201 by PECVD, followed by CMP, as shown in fig. 8.
In the second step, the silicon oxide layer is patterned to form a plurality of first trenches 203, as shown in fig. 9.
Third, a first layer of germanium 204 is selectively epitaxially grown on the patterned silicon oxide layer and then CMP is performed until it is in a relaxed state, as shown in FIG. 10.
And fourthly, repeating the first step to the third step, and sequentially forming a second layer of silicon oxide 205 (with the morphology shown in FIG. 11), forming a second layer of channels 206 (with the morphology shown in FIG. 12, the second layer of channels and the first layer of channels are arranged in a staggered mode), and extending a second layer of germanium 207 (with the morphology shown in FIG. 13).
And fifthly, selecting another silicon wafer with a silicon oxide layer on the surface as a second substrate 208, bonding the silicon oxide layer with the semiconductor structure formed in the previous step by using the silicon oxide layer as a bonding interface, and taking the final germanium layer in the semiconductor structure in the fourth step as the bonding interface, wherein the shape is shown in fig. 14.
Sixthly, etching to remove the sacrificial layer: etching to leave only the second substrate and the final germanium layer and planarizing to obtain the GOI structure, the topography shown in fig. 15.
The invention may also include in the fourth step, from the first step to the third step, a plurality of times until the defect density of the final germanium layer is no longer reduced, these embodiments being included in the invention, and preferably with a staggered arrangement between the channels of adjacent layers. For example, when the process is repeated 1 time, the profile shown in fig. 16 is formed, and then the sacrificial layer is bonded to the second substrate and removed.
The embodiments of the present disclosure have been described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be devised by those skilled in the art without departing from the scope of the present disclosure, and such alternatives and modifications are intended to be within the scope of the present disclosure.