JPH03104224A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To compose a uniform thin film of one of two stacked silicon wafers by selectively lapping the wafer with a silicon dioxide used as a stopper. CONSTITUTION:The surfaces of first and second silicon wafers 1 and 2 are oxidized to form an insulating film 3. These silicon wafers are heated and joined. The first wafer 1 is lapped and covered with silicon nitride 4. The silicon nitride layer 4 is coated with a resist layer 5, which is patterned and removed in the areas for forming grooves, before the silicon nitride layer 4 is dry-etched. The silicon wafer 1 is dry-etched to form grooves 6 that reach the insulating film 3, and then the grooves 6 is coated with silicon nitride 7 on their side walls. The insulating film 3 is etched away to expose the second silicon wafer 2. Silicon dioxide 8 is applied to the bottoms of the grooves 6. After the silicon nitride 7 is removed, the silicon wafer 1 is selectively lapped. According to this process, the silicon wafer is turned to be a uniform thin film at the same level as the silicon dioxide 8.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of the manufacturing method of Sol (silicon-on-insulator) substrates, the present invention concerns the improvement of the manufacturing method of Sol (silicon-on-insulator) substrates. The purpose of the present invention is to provide a method for manufacturing a laminated ultra-thin film So1 substrate with a high yield by thinning the film to a uniform thickness without causing any damage. The first silicon wafer or the second silicon wafer is partially removed to form a groove, a silicon nitride film is formed on the side wall of the groove, and the silicon nitride film is A silicon dioxide layer is formed in the groove formed on the side wall, the silicon nitride film is removed, and the silicon dioxide layer is used as a stopper to form the first silicon wafer or the second silicon wafer. The wafer is selectively polished to reduce its thickness. [Industrial Application Field] The present invention relates to an improvement in a method for manufacturing a Sol (silicon-on-insulator) substrate. [Prior Art] Compared to bulk substrates, SOI substrates are characterized in that elements can be easily separated, and the characteristics of the formed elements are also excellent. Among these, bonded SOI substrates that can take advantage of bulk crystallinity are attracting attention because of their excellent performance. This bonded Sol substrate is manufactured by oxidizing the surfaces of the first silicon wafer 1 and the second silicon wafer 2 to form an insulating film 3, as shown in FIG. 2(a).
As shown in b), the two are overlapped with an insulating layer 3 interposed therebetween and bonded through heat treatment, and as shown in the same figure (C),
One of the silicon wafers, for example, the first silicon wafer 1, has a reduced thickness, and devices are formed on this silicon layer with reduced thickness. On the other hand, the thinner the silicon layer on which the element is formed, the more
Since the performance of the LSI that is formed into the device will improve, ultra-thin S
OI substrates have attracted attention in recent years. In this case, it is necessary to suppress the in-plane variation in the thickness of the silicon layer on which the element is formed to less than the variation in the thickness of the supporting substrate. It is impossible to make wafers thinner. The conventional technology for thinning one side of bonded silicon wafers is explained below. As shown in FIG. 3(a), a first silicon wafer l and a second silicon wafer 2 are pasted together with an insulating film 3 interposed therebetween, and one of the silicon wafers, for example, the first silicon wafer l, Grind it and form it to a thickness that is not less than the thickness required for element formation. Next, as shown in FIG. 2B, the first silicon wafer 1 and the insulating film 3 are patterned to form grooves 6. Next, thermal oxidation is performed using the silicon nitride mask used in the previous step (buttering step) to form a silicon dioxide layer 9 in the groove 6, as shown in FIG. Observe formal precepts. When selective polishing is performed using an abrasive whose polishing rate for silicon dioxide is extremely lower than that for silicon, a silicon dioxide layer 9 formed at the bottom of the groove 6 is formed.
The upper surface functions as a stopper, and as shown in FIG. The film is made thinner. The silicon oxide layer peels off from the first silicon wafer 1, and the pieces of the peeled silicon dioxide mix into the polishing agent and damage the surface of the first silicon wafer 1 being polished. In addition, the peeled silicon dioxide particles adhere to the surface of the first silicon wafer 1 to be polished and remain without being removed even after cleaning.
As a result, this So! The manufacturing yield when devices are formed on the substrate decreases significantly. The purpose of the present invention is to eliminate this drawback, and to solve this problem, two
An object of the present invention is to provide a method for manufacturing a laminated ultra-thin film Sol substrate with a high yield by thinning one side of a silicon wafer to a uniform thickness without damaging or contaminating its surface. [Problem to be Solved by the Invention] By the way, when selectively polishing one of the two silicon wafers 8 bonded together, for example, the first silicon wafer 1, some of the silicon dioxide layer 9 formed in the groove 6 ,
[Means for Solving the Problem] The above purpose is to connect the first silicon wafer (1) and the second silicon wafer (2) via the insulating film (3). The first silicon wafer (1) or the second silicon wafer (2) is removed from a partial region to form a groove (6), and the side walls of the groove (6) are nitrided. A silicon film (7) is formed, and a silicon dioxide layer (8) is formed in the trench (6) formed on the side wall of the silicon nitride film (7).
), the silicon nitride III (7) is removed, and the first silicon wafer (1) or the second silicon wafer (2) is heated using the silicon dioxide layer (8) as a stopper. This is achieved by a method of manufacturing a semiconductor device that includes a step of selectively polishing to reduce its thickness. [Function] In the method for manufacturing a bonded SOI substrate according to the present invention, a groove 6 is formed in the first silicon wafer 1 or the second silicon wafer 2, and after forming a silicon nitride film 7 on the side wall of the groove 6. Since the silicon dioxide layer 8 is formed in the trench 6, the silicon dioxide layer 8 is formed only at the bottom of the trench 6 and not on the sidewalls of the trench 6. Moreover, in the method for manufacturing a bonded Sol substrate according to the present invention, after removing the silicon nitride II7 formed on the side wall of the groove 6, the first silicon wafer 1 or the second silicon wafer 2 is polished. This is true, and when polishing the first silicon wafer 1 or the second silicon wafer 2, there are no side walls of the groove. Therefore, when selectively polishing the first silicon wafer 1 or the second silicon wafer 2 using the silicon dioxide layer 8 as a stopper, in the prior art, the silicon dioxide layer that formed the sidewalls of the groove is completely removed. Since it does not exist in the present invention, it is impossible for it to peel off, and therefore, the silicon wafer surface cannot be damaged or contaminated by silicon dioxide particles that existed in the prior art but are not present in the present invention. This is impossible, and the silicon wafer is uniformly thinned to the same height as the surface of the silicon dioxide layer 8. [Example] Hereinafter, a method for manufacturing a bonded SOI substrate according to an example of the present invention will be described with reference to drawings. Refer to FIG. 1(a), the surfaces of the first silicon wafer 1 and the second silicon wafer 2 are oxidized to form an insulating film 3, and both are coated with the insulating film 3.
1,10 in an oxygen atmosphere.
After bonding by heating to a temperature of 0°C, one silicon wafer, for example, the first silicon wafer l, is ground to reduce its thickness to about 2n. Refer to FIG. 1(b) A silicon nitride layer 4 is formed on a first silicon wafer 1 using the CVD method, a resist layer 5 is formed thereon, and patterning is performed using a photolithography method. , the resist N5 is removed from above a certain groove-shaped region, and the silicon nitride layer 4 is dry etched using carbon tetrafluoride gas using the remaining resist layer 5 as a mask, and then the silicon nitride layer 4 is etched using carbon tetrachloride or the like. The silicon wafer 1 of 1 is dry-etched to form a groove 6 reaching the insulating film 3.See FIG. Silicon nitride film 7 with a thickness of about 5 nm on the side wall
Formally admonish. Referring to FIG. 1(d), the insulating film 3 exposed in the groove 6 is removed by etching using hydrofluoric acid to expose the second silicon wafer 2. Refer to FIG. 1(e). Heat to about 100° C. to thermally oxidize the second silicon wafer 2 exposed in the groove 6 to form a silicon dioxide layer 8 at the bottom of the groove 6. Note that this silicon dioxide layer 8
is formed so that its surface is, for example, approximately 0.5 nm higher than the surface where the insulating film 3 contacts the first silicon wafer 1. Referring to FIG. 1(f), the silicon nitride layer 4 formed on the first silicon wafer 1 and the silicon nitride film 7 formed on the side walls of the groove 6 are removed using hot phosphoric acid, and ethylenediamine and colloidal When the first silicon wafer 1 is selectively polished using a selective polishing method using a mixture of silica and silica as an abrasive, the silicon dioxide layer 8 functions as a polishing agent, and the first silicon wafer 1 is The difference in height between the surface of the insulating film 3 and the surface of the insulating film 3 in contact with the first silicon wafer l is approximately 0. The film is uniformly thinned to a thickness of 5 nm.
Note that the polishing rate ratio of silicon to silicon dioxide in the above polishing agent is 500:1, and the silicon dioxide layer B sufficiently functions as a stopper. [Effects of the Invention] As explained above, in the method for manufacturing a semiconductor device according to the present invention, after forming a silicon nitride film on the side wall of a groove formed in a first silicon wafer or a second silicon wafer, Since a silicon dioxide layer is formed in the groove as a stopper for selective polishing, this silicon dioxide layer is formed only on the bottom of the groove and not on the sidewalls of the groove. Moreover, in the method for manufacturing a bonded SOI substrate according to the present invention, the first silicon wafer or the second silicon wafer is polished after removing the silicon nitride film formed on the side wall of the groove. Therefore, when polishing the first silicon wafer or the second silicon wafer, there are no individual walls of the groove. Therefore, in the process of selectively polishing the first silicon wafer 1 or the second silicon wafer 2 using the silicon dioxide layer as a stopper, the silicon dioxide layer that existed on the sidewalls of the groove in the conventional technique is completely removed. Since it does not exist in the invention, it is impossible for this to peel off.
Therefore, the surface of the silicon wafer (thinned silicon wafer) is not damaged or contaminated by silicon dioxide particles that existed in the prior art but are not present in the present invention, and the silicon wafer is Since the film is uniformly thinned to the same height as the surface of the silicon dioxide layer 8, it is possible to improve the production yield of surface-bonded ultra-thin film SOI substrates.

[Brief explanation of drawings]

FIGS. 1(a) to 1(f) are manufacturing process diagrams of a Sol substrate according to an embodiment of the present invention. FIG. 2 is an explanatory diagram of a bonded Sol substrate. FIG. 3 is a manufacturing process diagram of an SOI substrate according to the prior art. Figure 1 of the present invention (a) lth silicon wafer, second silicon wafer, insulating film, silicon nitride layer, resist layer, groove, silicon nitride film, . . . silicon dioxide layer. Figure 1 (b) of the present invention

Claims (1)

[Claims] A first silicon wafer (1) and a second silicon wafer (2) are bonded via an insulating film (3); The silicon wafer (2) is removed from a partial area to form a groove (6).
forming a silicon nitride film (7) on the side wall of the groove (6); and forming a silicon nitride film (7) on the side wall of the groove (6).
), the silicon nitride film (7) is removed, and the silicon dioxide layer (8) is used as a stopper to form a silicon dioxide layer (8) in the first silicon wafer (1) or the second silicon wafer. A method for manufacturing a semiconductor device, comprising the step of selectively polishing a wafer (2) to reduce its thickness.