JP3371245B2 - Silicon substrate processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method of processing a silicon substrate, and more particularly to a method of forming a groove or a step on a silicon substrate by etching. Related to processing method. 2. Description of the Related Art As one example of a conventional silicon substrate processing method, a silicon substrate processing method for forming two types of grooves having different depths in a silicon substrate will be described. FIG. 4 is a flowchart showing a processing step in the conventional example, and FIGS. 5 and 6 are side sectional views showing a processing state on a silicon substrate in the processing step. Hereinafter, the conventional silicon processing method will be described with reference to FIGS. 4, 5 and 6. FIG. Referring to FIG. 4, first, in step 401, a film thickness defined as an etching mask pattern is formed on a silicon substrate 11 to be processed in correspondence with formation of a deeper one of two types of grooves. An oxide film 12 is formed on the upper surface, and an oxide film 13 is formed on the lower surface at the same time.
(A)). Next, in step 402, an oxide film etching mask pattern is formed on the upper surface of the oxide film 12 with the photoresist 14 in correspondence with the formation of the deeper groove (see FIG. 5B). In step 403, the oxide film 12 other than the oxide film 12 masked by the photoresist 14 is removed by oxide film etching, and an oxide film mask pattern of the oxide film 12 is formed on the upper surface of the silicon substrate 11. (See FIG. 5C).
Next, in step 404, a groove having a depth corresponding to the difference between the depth of the deep groove and the depth of the shallow groove is formed on the side of the deep groove of the silicon substrate 11 by silicon etching. Also, the layers 13 and 13 are thinned by etching by the amount corresponding to the difference in the etching rate (see FIG. 5D). In step 405, the photoresist 15 is formed corresponding to the formation of the shallower groove.
As a result, an oxide film mask pattern is produced (FIG. 6).
(A)). In step 406, the oxide film other than the oxide film 12 masked by the photoresist 15 is removed by oxide film etching, and an oxide film mask pattern of the oxide film 12 is formed corresponding to the silicon substrate 11. (See FIG. 6B). And step 40
In FIG. 7, two grooves each having a desired shape and depth are formed in the silicon substrate 11 by silicon etching, and at the same time, the oxide films 12 and 13 are also thinned by etching (FIG. 6). (See (c)), a series of processing for the silicon substrate is completed. The etching process in the conventional silicon substrate processing method is performed in consideration of a difference in an etching rate between an oxide film and a silicon substrate. In the above-described conventional method for processing a silicon substrate, a deep groove (or step) is formed.
In the course of the silicon etching corresponding to the above, a groove having a depth corresponding to the difference between the depths of the grooves is formed on the silicon substrate, and then an etching mask pattern corresponding to the shallower groove is formed. As shown in FIG. 6A, in step 405, a photoresist for performing a patterning process may be applied to the silicon substrate 11 having a step due to the groove. It is an indispensable condition. Usually, a photoresist is applied to a silicon substrate by a spin coating method in which a photoresist dropped at the center of the silicon substrate is formed by rotating the silicon substrate and spreading it over the entire silicon substrate by centrifugal force. When the depth of the groove to be formed becomes deep,
Since the photoresist is repelled at the edge of the groove, the production state of the etching mask pattern formed by the photoresist deteriorates, which is a factor that causes a problem in producing the etching mask pattern corresponding to the shallower groove. I have. For this reason, the conventional silicon substrate processing method has a drawback that it is extremely difficult to form two types of grooves having a large difference in groove depth on the silicon substrate. [0005] In the silicon processing method,
By forming a groove corresponding to the crystal orientation, a patterning step is performed on a silicon substrate having reduced strength, and there is a concern that the silicon substrate may be damaged in the course of the step. In particular, when the steps such as grooves having different depths increase, the number of steps increases accordingly, and there is a disadvantage that the risk of damaging the silicon substrate further increases. [0006] The object of the present invention is to eliminate the above disadvantages,
A method of processing a silicon substrate, which can easily perform a process of forming a groove having a great difference in depth on a silicon substrate and further eliminates a fear of damage to the silicon substrate during the processing process. Is to provide. A method of processing a silicon substrate according to the present invention is a method of processing a silicon substrate, wherein grooves having different processing depths are formed in the silicon substrate. A first step of forming a first oxide film etching mask pattern relating to the formation of only the shallow first groove, and a specific step defined by processing conditions on the first oxide film etching mask pattern. A second step of forming a second oxide film having a thickness T;
Forming a second oxide film etching mask pattern for forming a second groove having a deeper processing depth on the oxide film, and etching the first and second grooves. Forming a groove having a predetermined shape and a predetermined depth on the silicon substrate. [0008] The first step is a step of forming a first oxide film on the silicon substrate with a thickness required for forming the first oxide film etching mask pattern; Forming a first oxide film etching mask pattern on the first oxide film with a photoresist, and forming the first oxide film on the silicon substrate by the oxide film etching; Forming an oxide film etching mask pattern. The specific thickness T of the second oxide film formed in the second step is defined by the following equation. T = (D 2 −D 1) × RSi 02 / RSi D 1: Processing depth of the first groove D 2: Processing depth of the second groove RSi 02: Oxide film etching rate RSi: Silicon etching rate Forming a second oxide film etching mask pattern on the second oxide film by using a photoresist;
Forming the second oxide film etching mask pattern using the second oxide film on the silicon substrate. According to the above-described silicon processing method, it is not necessary to provide a step of forming a mask pattern for the shallower groove during the etching process corresponding to the deeper groove. This eliminates the problem associated with the formation of the mask pattern corresponding to the shallower groove, and makes it possible to easily perform silicon etching even when the difference in groove depth is large. In addition, since the number of patterning processes for the silicon substrate whose strength has been reduced due to the formation of the groove is reduced, the possibility of damage to the silicon substrate during the processing process is eliminated. Next, the present invention will be described with reference to the drawings. According to an embodiment of the present invention, when grooves having different depths are formed in a silicon substrate, the first oxide film etching corresponding to the formation of the shallower grooves is performed on the silicon substrate. Forming a mask, forming a second oxide film having a specific thickness on the first oxide film etching mask, and forming a second oxide film having a greater depth on the second oxide film. A step of forming a second oxide film etching mask corresponding to the formation of the groove, and silicon etching to form both the shallower groove and the deeper groove into a desired shape and a desired depth, respectively. Forming a groove on the silicon substrate. FIG. 1 is a view showing a flowchart of a processing step of one example of the present embodiment. FIG. 2 and FIG. 3 are side sectional views showing a processing state on the silicon substrate in the processing step. In the following, FIG.
With reference to FIGS. 2 and 3, the silicon processing method of the present embodiment will be described. Referring to FIG. 1, first, in step 101, an oxide film etching mask pattern is defined on a silicon substrate 1 to be processed, corresponding to the formation of a shallower of the two types of grooves. An oxide film 2 having a thickness is formed on the upper surface, and at the same time, an oxide film 3 is formed on the lower surface (see FIG. 2A). In this step 101, as described above, the thickness of the oxide film 2 is defined so as to be an appropriate thickness as an oxide film etching mask pattern, particularly when silicon is etched on the silicon substrate 1. Next, in step 102, a first oxide film etching mask pattern is formed on the upper surface of the oxide film 2 with the photoresist 4 in correspondence with the formation of the shallow groove (see FIG. 2B). In step 103, the oxide film other than the oxide film 2 masked by the photoresist 4 is removed by the oxide film etching, and a first oxide film etching mask of the oxide film 2 is formed on the upper surface of the silicon substrate 1. A pattern is formed (see FIG. 2C). Next, in step 104, an oxide film 5 having a thickness T defined by the following arithmetic expression is formed on the first oxide film etching mask pattern by the oxide film 2, and at the same time, an oxide film 6 is formed on the lower surface. The film is formed (see FIG. 2D). In the following formula, D1 <D2 and RSiO2 <RSi. T = (D 2 −D 1) × R SiO 2 / R Si D 1: processing depth of shallow groove D 2: processing depth of deep groove RSiO 2: oxide film etching rate R Si: silicon etching rate Corresponds to the formation of a deep groove on the upper surface of the oxide film 5,
The oxide film etching mask pattern of FIG.
(A)). In step 106, the oxide film other than the oxide film 5 and the oxide film 2 masked by the photoresist 7 is removed by oxide film etching, and the upper surface of the silicon substrate 1 is covered with the oxide film 5 and the oxide film 2. Second
The oxide film etching mask pattern of FIG.
(B)). Next, in step 107, the oxide film 5 is removed by silicon etching, and a deeper groove is formed on the upper surface of the silicon substrate 1 as a groove having a depth corresponding to the difference between the two grooves. Oxide film 2
An oxide film etching mask pattern is formed (see FIG. 3C). Further, two grooves each having a desired shape and depth are formed in the silicon substrate 1 by the continuous silicon etching process (see FIG. 3D). That is, in this embodiment, the thickness of the second oxide film etching mask pattern is defined by the difference between the etching rates of the oxide film and silicon during silicon etching and the processing depth of the groove. As a condition, prior to the step of forming a groove in the silicon substrate by silicon etching, patterning processing for forming an oxide film etching mask pattern corresponding to the formation of the groove is performed from the shallower groove, Further, by performing all the procedures of forming an oxide film of a predetermined thickness again on the oxide film etching mask pattern and successively performing the same patterning processing sequentially, all disadvantages of the conventional silicon processing method are eliminated. Be eliminated. In general, the present invention is not limited to the case where the number of grooves having different depths is two as in the present embodiment, and also the case where three or more grooves are formed in a silicon substrate by applying the present invention.
Prior to the step of forming grooves in the silicon substrate by silicon etching, the patterning step of forming a required oxide film etching mask pattern corresponding to the formation of all the grooves is completed, whereby the plurality of grooves are formed. The formation can be easily performed, and a situation in which the silicon substrate is damaged can be suppressed. As described above, the present invention is applied to a silicon substrate processing method for forming grooves having different processing depths in a silicon substrate, and oxidizes in response to the formation of the grooves. The step of forming a film etching mask pattern is performed sequentially from the shallower groove, and prior to the step of forming a groove in a silicon substrate by silicon etching, a patterning step related to formation of all oxide film etching mask patterns Is completed, a step of forming a groove on the silicon substrate over time, and thereafter, forming an etching mask pattern by a photoresist on the silicon substrate having a step due to the groove is eliminated. . Thereby, there is an effect that it is extremely easy to form two types of grooves having a large difference in groove depth in the silicon substrate. In addition, since the number of steps for forming grooves corresponding to the crystal orientation in the silicon substrate is reduced, there is an effect that the fear of damage to the silicon substrate during the processing step can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a flowchart of a process according to one embodiment of the present invention. FIG. 2 is a side sectional view (1) of a silicon substrate showing a processing state in each step of the embodiment. FIG. 3 is a side sectional view (2) of the silicon substrate showing a processing state in each step of the embodiment. FIG. 4 is a diagram showing a flowchart of a process of a conventional example. FIG. 5 is a side sectional view (1) of a silicon substrate showing a processing state in each step of the conventional example. FIG. 6 is a side sectional view (2) of the silicon substrate showing a processing state in each step of the conventional example. [Description of Signs] 1,11 Silicon substrate 2,3,5,6,12,13 Oxide film 4,7,14,15 Photoresist

Claims (1)

(1) In a silicon substrate processing method for forming grooves having different processing depths in a silicon substrate, the first processing method includes the step of forming a first shallower processing depth on the silicon substrate.
A first step of forming a first oxide film etching mask pattern relating to the formation of only the groove, and a second step of forming a second film having a specific film thickness T defined by processing conditions on the first oxide film etching mask pattern. A second step of forming an oxide film, and a third step of forming, on the second oxide film, a second oxide film etching mask pattern related to formation of a second groove having a deeper processing depth. And a fourth step of forming the first and second grooves in the silicon substrate as grooves having a predetermined shape and a predetermined depth, respectively, by etching. Forming, on the silicon substrate, a first oxide film having a thickness required to form the first oxide film etching mask pattern; By the photoresist, the first Forming an oxide film etching mask pattern; and forming the first oxide film etching mask pattern by the first oxide film on the silicon substrate by oxide film etching. The specific thickness T of the second oxide film formed in the step is defined by the following equation: T = (D2−D1) × RSi02 / RSiD1: Processing depth D1 of first groove: Processing depth RSi02 of second groove: oxide film etching rate RSi: silicon etching rate In the third step, the second oxide film etching mask pattern is formed on the second oxide film using a photoresist. And forming the second oxide film etching mask pattern with the second oxide film on the silicon substrate by oxide film etching. Silicon substrate processing method according to claim.