Forming condition determination method of oxide film, formation method of oxide film and manufacturing method of wafer

Abstract

To provide a forming condition determination method of an oxide film in which an oxide film having a desired film thickness distribution on a wafer can be formed.SOLUTION: A forming condition determination method of an oxide film comprises: a previous oxide film formation step that forms a first oxide film on a first wafer using a first tray body; a correlation relationship acquisition step that acquires a correlation relationship between at least one constitution requirement of a groove part and a contact part of a tray body, and film thickness distribution of an oxide film; a target film thickness distribution acquisition step that acquires target film thickness distribution of the oxide film; and a tray body constitution determination step that determines the at least one constitution requirement which can form the oxide film of the target film thickness distribution as an application requirement on the basis of film thickness distribution of the first oxide film and the correlation relationship.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for determining conditions for forming an oxide film, a method for forming an oxide film, and a method for manufacturing a wafer. [Background technology]

[0002] 2. Description of the Related Art A method is known in which an oxide film is formed on a wafer by supplying a source gas onto the wafer placed on a film formation tray while heating the film formation tray (see, for example, Patent Document 1). The film formation tray described in Patent Document 1 includes a support member that supports the outer periphery of a wafer and a tray body that supports the support member. Patent Document 1 describes that the thickness distribution of an oxide film on a wafer can be made more uniform by reducing the contact area between the support member and the tray body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Re-tabled publication No. 2011 / 070741 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, with the demand for a more uniform film thickness distribution, variations in film thickness distribution among a plurality of film forming apparatuses have become a problem.

[0005] An object of the present invention is to provide a method for determining oxide film formation conditions, a method for forming an oxide film, and a method for manufacturing a wafer, which are capable of forming an oxide film having a desired film thickness distribution on a wafer. [Means for solving the problem]

[0006] The method for determining oxide film formation conditions of the present invention is a method for determining conditions for forming an oxide film on a wafer using a film formation apparatus, the film formation apparatus using a film formation tray including a support member for supporting an outer periphery of the wafer and a tray body for supporting the support member, and forming the oxide film on the wafer by supplying a source gas onto the wafer while heating the film formation tray, the support member including a ring-shaped mounting portion on which the wafer is placed and legs extending downward from the mounting portion, the tray body including a cylindrical recess for accommodating the support member and a plurality of grooves formed along an outer edge of a bottom surface of the recess, The method for determining conditions for forming an oxide film includes a pre-oxide film formation process for forming a first oxide film on the first wafer using the first tray body, a correlation acquisition process for acquiring a correlation between at least one constituent element of the grooves and the contact portions and a thickness distribution of the oxide film, a target thickness distribution acquisition process for acquiring a target thickness distribution of the oxide film, and a tray body configuration determination process for determining, as an applicable requirement, the at least one constituent element capable of forming the oxide film of the target thickness distribution based on the thickness distribution of the first oxide film and the correlation.

[0007] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the correlation includes a first correlation between the width of at least a portion of the groove portion in the circumferential direction and the thickness of the oxide film in a region adjacent to the at least a portion in the outer periphery of the wafer.

[0008] In the method for determining conditions for forming an oxide film of the present invention, the film formation apparatus is configured to line up a plurality of film formation trays, each of which has the tray body, in a feed direction and transport them in the feed direction, while forming the oxide film on the wafer supported on each film formation tray, and it is preferable that the correlation includes a second correlation between a contact area between the contact portion and the leg portion at a portion of the tray body on the transport width direction side perpendicular to the feed direction, and a thickness of the oxide film in a region adjacent to the portion on the transport width direction side at the outer periphery of the wafer.

[0009] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the second correlation is such that the larger the contact area at the portion on the transport width direction side, the thinner the oxide film in the region adjacent to the portion on the transport width direction side.

[0010] In the method for determining conditions for forming an oxide film of the present invention, the film formation apparatus is configured to line up a plurality of film formation trays, each of which has the tray body, in the feed direction and transport them in the feed direction, while forming the oxide film on the wafer supported on each film formation tray, and it is preferable that the correlation includes a third correlation between the contact area of ​​the contact portion and the leg portion at the feed direction side and the opposite direction side of the tray body relative to the feed direction, and the thickness of the oxide film in a region adjacent to the feed direction side and the opposite direction side of the outer periphery of the wafer.

[0011] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the third correlation is such that the larger the contact area at the portions on the feed direction side and the opposite direction side, the thicker the oxide film in the regions adjacent to the portions on the feed direction side and the opposite direction side.

[0012] The oxide film forming method of the present invention includes a step of performing the above-mentioned oxide film formation condition determination method, and a film forming step of forming a second oxide film on a second wafer using a second tray body that satisfies the application requirements.

[0013] In the oxide film forming method of the present invention, it is preferable that the method further includes a tray body preparation process for preparing multiple types of tray bodies each differing from the other in at least one constituent element, and the film forming process includes selecting the second tray body from the at least one constituent element corresponding to each of the multiple types of tray bodies, and forming the second oxide film using the second tray body.

[0014] The method for producing a wafer of the present invention includes a step of forming an oxide film on the second wafer by the above-mentioned method for forming an oxide film. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing a configuration of a film forming apparatus according to a prerequisite technique of the present invention; [Diagram 2] 1A and 1B are diagrams showing the configuration of a film formation tray according to the base technology and experimental examples 1 and 2, in which (A) is a plan view, (B) is a view taken along line IIB-IIB in (A), and (C) is a view taken along line IIC-IIC in (A). [Diagram 3] 1A and 1B are plan views showing tray bodies according to experimental examples, where (A) shows the tray body of experimental example 3, and (B) shows the tray body of experimental example 4. FIG. [Figure 4] FIG. 1 is a schematic diagram showing the evaluation area of ​​the film thickness used in the method for investigating the correlation between the structural requirements of the groove and contact parts of the tray body and the film thickness distribution of the oxide film, where (A) shows the central area, (B) shows the outer peripheral area, (C) shows the transport width direction area, and (D) shows the transport direction area. [Diagram 5] 2 is a flowchart showing a method for manufacturing a wafer according to an embodiment of the present invention. [Figure 6] 4 is a flowchart showing an oxide film forming process according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Prerequisite technology] First, before describing an embodiment of the present invention, a configuration of a film forming apparatus used in the embodiment will be described. Fig. 1 is a schematic diagram showing the configuration of a film forming apparatus according to a prerequisite technique of the present invention. 1 forms an oxide film on a wafer W. The film forming apparatus 1 includes a plurality of film forming trays 2, a circulation unit 3, and a film forming unit 4. The wafer W may be made of a material such as silicon, germanium, gallium arsenide, gallium phosphide, or indium phosphide.

[0017] The film formation tray 2 accommodates the wafers W. A detailed configuration of the film formation tray 2 will be described later.

[0018] The circulation unit 3 circulates a predetermined number of film formation trays 2 within the film formation apparatus 1. The circulation unit 3 includes a first lifting unit 31, a film formation transport unit 32, a second lifting unit 33, and a return transport unit .

[0019] The first lifting section 31 includes a first lift 311 on which the film formation tray 2 is placed, and a first lifting drive section 312 that raises and lowers the first lift 311. When the first lift 311 is in the raised position, the wafer W before film formation is transferred into the film formation tray 2 by a transfer section (not shown), and the film formation tray 2 is delivered to the film formation transport section 32. The structure for delivering the film formation tray 2 from the first lift 311 to the film formation transport section 32 is not particularly limited, and a well-known structure can be applied.

[0020] The film formation conveying section 32 includes a pair of conveying rollers 321 and a conveying belt 322 stretched over the pair of conveying rollers 321. The film formation conveying section 32 rotates the conveying belt 322 in a clockwise direction in FIG. 1 by the rotation of the conveying rollers 321, thereby conveying the multiple film formation trays 2 in contact with each other to the film formation section 4. An example of a configuration in which the conveying belt 322 conveys the film formation trays 2 may be a configuration in which protrusions provided on the conveying belt 322 are fitted into fitting grooves provided on the lower surface of the tray body 22. The direction in which the film formation conveying section 32 conveys the film formation trays 2 may be referred to as a "feed direction". In addition, a direction perpendicular to the feed direction and the vertical direction may be referred to as a "transport width direction".

[0021] The second lifting section 33 includes a second lift 331 on which the film formation tray 2 is placed, and a second lifting drive section 332 for raising and lowering the second lift 331. When the second lift 331 is in the raised position, the film formation tray 2 containing the wafer W after film formation is transferred from the transport rollers 321 to the second lift 331. When the second lift 331 is in the lowered position, the film formation tray 2 containing the wafer W after film formation is transferred to the return transport section 34. The structure for transferring the film formation tray 2 from the transport rollers 321 to the second lift 331 and the structure for transferring the film formation tray 2 from the second lift 331 to the return transport section 34 are not particularly limited, and a well-known structure can be applied.

[0022] The return transport section 34 transports the film formation tray 2 containing the wafers W after film formation in the direction opposite to the sending direction. The film formation tray 2 transported by the return transport section 34 is handed over to the first lift 311 located at the lowered position. The structure for handing over the film formation tray 2 from the return transport section 34 to the first lift 311 is not particularly limited, and a well-known structure can be applied. The direction in which the return transport section 34 transports the film formation tray 2 may be referred to as the "return direction".

[0023] When the film formation tray 2 is delivered from the return transport unit 34 at the lowered position, the first lift 311 rises to the upper position. When the first lift 311 is in the upper position, the wafer W after film formation is transferred from the film formation tray 2 to a wafer storage unit (not shown) by the transfer unit. Thereafter, as described above, the wafer W before film formation is transferred into the film formation tray 2 by the transfer unit (not shown), and the film formation tray 2 is delivered to the film formation transport unit 32.

[0024] The film formation unit 4 forms an oxide film on the wafer W in the film formation tray 2 transported by the film formation transport unit 32. The film formation unit 4 includes a preheater 41, a heater 42, a raw material gas supply unit 43, a pair of blocking gas supply units 44, and a pair of exhaust units 45.

[0025] The preheater 41 and the heater 42 are disposed, for example, in a space surrounded by the conveyor belt 322. The heater 42 is disposed on the feed direction side of the preheater 41. The wafer W in the film formation tray 2 is preheated by the preheater 41 to a temperature lower than the film formation temperature, and then heated by the heater 42 to the film formation temperature.

[0026] The source gas supply unit 43 is disposed above the heater 42. The source gas supply unit 43 ejects the source gas G1 downward and supplies it onto the wafer W. An oxide film is formed by reaction on the heated wafer W. Examples of the source gas include a mixed gas of monosilane (SiH4) and oxygen (O2), or a mixed gas of tetraethoxysilane (TEOS, chemical formula: Si(OC2H5)4) and ozone (O3).

[0027] The pair of insulating gas supply units 44 are disposed above the heater 42 on the feed and return sides, respectively, of the raw material gas supply unit 43. Each insulating gas supply unit 44 ejects insulating gas G2 downward to prevent the raw material gas G1 from leaking in the feed and return directions relative to the film forming unit 4. An example of the insulating gas G2 is nitrogen gas.

[0028] The pair of exhaust units 45 are respectively disposed between the raw material gas supply unit 43 and the blocking gas supply unit 44 on the feed direction side, and between the raw material gas supply unit 43 and the blocking gas supply unit 44 on the return direction side. Each exhaust unit 45 exhausts the blocking gas G2 and the raw material gas G1 not used in film formation from the space between the raw material gas supply unit 43 and the film formation tray 2 to above the raw material gas supply unit 43.

[0029] Next, a detailed configuration of the film formation tray 2 will be described. Fig. 2 is a diagram showing the configuration of the film formation tray, (A) being a plan view, (B) being a view taken along line IIB-IIB in (A), and (C) being a view taken along line IIC-IIC in (A). 2(A) to 2(C), the film formation tray 2 includes a support member 21 and a tray body 22. The support member 21 and the tray body 22 are made of, for example, SiC.

[0030] The supporting member 21 supports the outer periphery of the wafer W. The supporting member 21 includes a mounting portion 211 and legs 212. The mounting portion 211 is formed in an annular shape. The wafer W is placed on the mounting portion 211. The leg portion 212 is formed so as to extend downward from the entire outer edge of the mounting portion 211 in a cylindrical shape.

[0031] The tray body 22 is formed in a rectangular parallelepiped shape. The side surface corresponding to the long side of the rectangle in the tray body 22 in the plan view shown in Fig. 2(A) constitutes an opposing surface 22A opposing the adjacent film formation tray 2 when transported by the film formation transport unit 32 of the film formation apparatus 1, as shown in Fig. 1, and the side surface corresponding to the short side constitutes a non-opposing surface 22B not opposing the adjacent film formation tray 2 when transported by the film formation transport unit 32 of the film formation apparatus 1. A cylindrical recess 221 is formed in the center of the tray body 22. A plurality of arc-shaped grooves 222 are formed along the outer edge of the bottom surface of the recess 221. A portion located between a pair of adjacent grooves 222 constitutes a contact portion 223 that supports the leg portion 212 of the support member 21.

[0032] [How the present invention was arrived at] Next, the circumstances that led to the invention will be described. An experiment was carried out to examine the correlation between the configuration requirements of the groove portion 222 and the contact portion 223 of the tray body 22 of the film formation tray 2 described above and the film thickness distribution of the oxide film on the wafer W. Fig. 3 is a plan view showing a tray body according to the experimental examples, (A) showing the tray body of experimental example 3, and (B) showing the tray body of experimental example 4. Fig. 4 is a schematic diagram showing an evaluation area of ​​the film thickness used in a method for investigating the correlation between the configuration requirements of the groove and contact parts of the tray body and the film thickness distribution of the oxide film, where (A) shows the central area, (B) shows the outer peripheral area, (C) shows the transport width direction area, and (D) shows the transport direction area.

[0033] <How to create an evaluation sample> First, four types of tray bodies 22 were prepared, each differing from the other in at least one of the constituent elements of the groove portion 222 and the contact portion 223, for example, the number, shape, and position. Specifically, tray bodies 23, 24, 25, and 26 were prepared in Experimental Examples 1, 2, 3, and 4 shown below. Note that the same names and symbols are used for the tray bodies 23, 24, 25, and 26 that have the same configuration as the tray body 22 in the background art described above, or that have the same configuration as each other.

[0034] The tray body 23 of Experimental Example 1 has the configuration shown in Figures 2(A) to 2(C). Six grooves 232 of the same shape are formed in the bottom surface of the recess 221 of the tray body 23. Each groove 232 is formed to have a (circumferential) length of L1. As shown in Table 1 below, each groove 232 is formed to satisfy the relationship of "J1:J0=4:1", where J1 is the width of the groove 232 and J0 is the width (thickness) of the leg 212 of the support member 21. Each groove 232 is formed at equal intervals so that six first contact portions 233 of the same shape are provided. The (circumferential) length of each of the first contact portions 233 thus provided is M1, as shown in Table 1.

[0035] [Table 1]

[0036] The tray body 24 of Experimental Example 2 has the configuration shown in Figures 2(A) to 2(C). Six grooves 242 of the same shape are formed in the bottom surface of the recess 221 of the tray body 24. The length of each groove 242 is L1, which is the same as the length of the groove 232 in Experimental Example 1. As shown in Table 1, when the width of the groove 242 is J2, each groove 242 is formed to satisfy the relationship of "J2:J0=6:1". The grooves 242 are formed at equal intervals so that the length of each first contact portion 243 is M1, which is the same as the length of the first contact portion 233 in Experimental Example 1.

[0037] The tray body 25 of Experimental Example 3 has the configuration shown in Fig. 3(A) .The tray body 25 has four grooves 252 of the same shape formed in the bottom surface of the recess 221. The length of each groove 252 is L2, which is longer than the length of the groove 232 in Experimental Example 1. The width of each groove 252 is J1, which is the same as the width of the groove 232 in Experimental Example 1. Each groove 252 is formed such that two first contact portions 233 and two second contact portions 254 are alternately arranged in the circumferential direction. When the length of the second contact portion 254 is M2, each second contact portion 254 is formed to satisfy the relationship of "M2:M1=52:1". The length M2 of the second contact portion 254 is shorter than the sum of the length M1 of the two adjacent first contact portions 233 in the tray body 23 in Experimental Example 1 and the length L1 of the groove portion 232 between the two adjacent first contact portions. Each groove 252 is formed so that the center of the length of each first contact portion 233 is located at a portion closest to the pair of non-opposing surfaces 22B in the recess 221, and the center of the length of each second contact portion 254 is located at a portion closest to the pair of opposing surfaces 22A in the recess 221. In other words, each groove 252 is formed so that one first contact portion 233 is located on each side in the conveying width direction, and one second contact portion 254 is located on each of the feed direction side and return direction side.

[0038] The tray body 26 of Experimental Example 4 has the configuration shown in Fig. 3(B) .On the bottom surface of the recess 221 of the tray body 26, two grooves 262 of the same shape are formed. The length of each groove 262 is L3, which is longer than the length of the groove 252 in Experimental Example 3. The width of each groove 262 is J1, which is the same as the width of the groove 232 in Experimental Example 1. Each groove 262 is formed so that the two second contact portions 254 are located at the same positions as the second contact portions 254 in Experimental Example 3. In other words, each groove 262 is formed so that one second contact portion 254 is located on each of the feed direction side and the return direction side.

[0039] In addition, ten wafers W each having a diameter of 300 mm were prepared. Then, seven film formation trays 2 each having the tray body 23 of Experimental Example 1 and one each of the film formation trays 2 each having the tray body 24, 25, 26 of Experimental Examples 2, 3, 4 were placed in the circulation section 3 of the film formation device 1, and an oxide film was formed on each of the wafers W by using the four film formation trays 2 each having the tray body 23, 24, 25, 26 of Experimental Examples 1, 2, 3, 4. The target thickness of the oxide film is 350 nm. Hereinafter, the wafers W on which the film formation was performed on the film formation trays 2 each having the tray body 23, 24, 25, 26 of Experimental Examples 1, 2, 3, 4 may be referred to as the wafers W1, W2, W3, W4 of Experimental Examples 1, 2, 3, 4, respectively.

[0040] <Method of investigating the correlation between the configuration requirements of the groove and contact parts of the tray body and the thickness distribution of the oxide film> (1. Correlation between the grooves in the tray body and the thickness distribution of the oxide film) The thickness distribution of the oxide film was measured for each of the wafers W1 and W2 of Experimental Examples 1 and 2. Then, the average thickness of the oxide film in the central region A1 shown in the top diagram of FIG. 4(A) and the peripheral region A2 shown in FIG. 4(B) for each of the wafers W1 and W2 was calculated. The central region A1 is a circular region with a diameter of 60 mm centered on the center of the wafer W. The peripheral region A2 is an annular region within 30 mm from the outer edge of the wafer W. The width of the peripheral region A2 is larger than the width J2 of the groove portion 242 in Experimental Example 2.

[0041] Next, the first film thickness ratios in the wafers W1 and W2 of Experimental Examples 1 and 2 were calculated based on the following formula (1). First thickness ratio = average thickness of the peripheral region / average thickness of the central region … (1) Then, a first influence evaluation value for evaluating the influence of the width of the groove portion was calculated based on the following formula (2). First influence evaluation value=First film thickness ratio on wafer W2 of Experimental Example 2 / First film thickness ratio in wafer W1 of Experimental Example 1 … (2) The calculation results of equations (1) and (2) are shown in Table 2.

[0042] [Table 2]

[0043] As shown in Table 2, the first impact assessment value was less than 1. From this, it was confirmed that there is a correlation between the width of the groove 222 and the thickness distribution of the oxide film, such that as the width of the groove 222 increases, the oxide film on the outer periphery of the wafer W becomes thinner than the oxide film in the center.

[0044] The present inventors speculate that the reason for such a correlation is as follows. The larger the width of the groove 222, the longer the distance from the inner edge of the groove 222 (the edge on the recess center side in a plan view) to the leg 212 of the support member 21, and the smaller the amount of heat transferred from the inner edge of the groove 222 to the outer periphery of the wafer W via the leg 212. It was presumed that when the amount of heat transferred to the outer periphery of the wafer W decreases, the temperature of the outer periphery decreases and the oxide film on the outer periphery becomes thinner. Moreover, from the above-mentioned estimation results, it is considered that the smaller the width of the groove 222, the thicker the oxide film on the outer periphery of the wafer W becomes relative to the oxide film in the central portion. It is also believed that by making the width of a portion of groove portion 222 in the circumferential direction larger or smaller than the width of the remainder, the oxide film in the portion adjacent to that portion can be made thinner or thicker than the oxide film in the portion adjacent to the remainder. That is, it was confirmed that there is a correlation (hereinafter, sometimes referred to as a "first correlation") between the width of at least a portion of the groove 222 in the circumferential direction and the ratio of the thickness of the oxide film in the region adjacent to said at least a portion in the outer periphery to the thickness of the oxide film in the center of the wafer W. The first correlation can also be said to be a correlation between the width of at least a portion of the groove 222 in the circumferential direction and the thickness of the oxide film in the region adjacent to said at least a portion in the outer periphery of the wafer W.

[0045] (2. Correlation between the presence or absence of contact areas in the width direction of the tray body and the thickness distribution of the oxide film) The thickness distribution of the oxide film was measured for each of the wafers W3 and W4 of Experimental Examples 3 and 4. Then, the average thickness of the oxide film in the central region A1 and the transport width direction region A3 shown in FIG. 4(C) was calculated for each of the wafers W3 and W4. The transport width direction region A3 is a substantially semicircular region on both ends of the wafer W in the transport width direction. The circumferential length of the transport width direction region A3 is 60 mm, which is longer than the length M1 of the first contact portion 233 of Experimental Example 3. The radial length of the transport width direction region A3 is 30 mm.

[0046] Next, the second film thickness ratios for wafers W3 and W4 of Experimental Examples 3 and 4 were calculated based on the following formula (3). The calculation results are shown in Table 3 below. Second film thickness ratio = average film thickness in the width direction / average film thickness in the central region … (3) Then, a second influence evaluation value for evaluating the influence of the presence or absence of a contact portion in the transport width direction was calculated based on the following formula (4). Second influence evaluation value=Second film thickness ratio on wafer W3 of Experimental Example 3 / Second film thickness ratio in wafer W4 of Experimental Example 4 … (4) The calculation results of equations (3) and (4) are shown in Table 3.

[0047] [Table 3]

[0048] As shown in Table 3, the second impact assessment value was less than 1. From this, it was confirmed that the presence or absence of the contact portion 223 in the transport width direction and the thickness distribution of the oxide film are correlated in that the oxide film in the region adjacent to the transport width direction side portion in the outer periphery of the wafer W is thinner than the central portion when the contact portion 223 is provided in the transport width direction side portion of the tray body 22 compared to when the contact portion 223 is not provided. Note that the transport width direction side portion of the tray body 22 where the contact portion 223 is provided is a portion within a sector area that includes the center 221C of the recess 221 and is symmetrical with respect to a reference line T1 parallel to the transport width direction and the vertical direction, with a central angle θ1 of 60°, as shown in FIG. Note that, normally, the center 221C of the recess 221 overlaps with the center Wc of the wafer W supported by the support member 21 in a plan view.

[0049] The present inventors speculate that the reason for such a correlation is as follows. During the formation of an oxide film on the wafer W in any film-forming tray 2, film-forming trays 2 are present on the feed direction side and return direction side of the film-forming tray 2 (hereinafter, the feed direction side and return direction side may be collectively referred to as "both sides in the transport direction"), but since no film-forming trays 2 are present on both sides in the transport width direction, it is considered that the temperature on both sides in the transport width direction of the tray body 22 is lower than that on both sides in the transport direction. For this reason, it is presumed that the heat on both sides in the transport width direction of the placement part 211 of the support member 21 is absorbed by the tray body 22 through the legs 212 and the contact parts 223 on both sides in the transport width direction, causing the temperature on both sides in the transport width direction of the wafer W to decrease, and the oxide film on both sides in the transport width direction to become thinner.

[0050] In addition, from the estimation results as described above, it is considered that the oxide film in the region adjacent to the portion on the outer periphery of the wafer W in the transport width direction will be thicker than the central portion when compared to when the contact portion 223 is not provided at the portion on the transport width direction side of the tray body 22. Furthermore, when the contact portion 223 is provided at a portion on the tray body 22 in the transport width direction, it is considered that heat on the transport width direction side of the tray body 22 is more likely to escape when the contact portion 223 is long than when it is short. For this reason, it is considered that as the contact portion 223 becomes longer and the contact area between the contact portion 223 and the leg portion 212 becomes larger, the oxide film on the portion adjacent to the portion on the transport width direction side at the outer periphery of the wafer W becomes thinner than the central portion. That is, it was confirmed that there is a correlation (hereinafter, sometimes referred to as a "second correlation") between the contact area between the contact portion 223 and the leg portion 212 at the portion on the tray body 22 in the transport width direction and the ratio of the thickness of the oxide film at the region adjacent to the portion on the transport width direction side at the outer periphery to the thickness of the oxide film at the center of the wafer W. The second correlation can also be said to be a correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the tray body 22 in the transport width direction and the thickness of the oxide film at the region adjacent to the portion on the outer periphery of the wafer W in the transport width direction.

[0051] (3. Correlation between the contact area between the contact part and the leg in the conveying direction of the tray body and the thickness distribution of the oxide film) The average thickness of the oxide film in the central region A1 and the two transport direction regions A4 shown in Fig. 4(D) of the wafers W of Experimental Examples 1 and 3 was calculated. The transport direction regions A4 are approximately arc-shaped regions on both sides of the wafer W in the transport direction. The circumferential length of the transport direction region A4 is 220 mm, which is longer than the length of the arc-shaped region including the two adjacent contact portions 223 of Experimental Example 1 and the length of one second contact portion 254 of Experimental Example 3. The width (radial length) of the transport direction region A4 is 30 mm.

[0052] Next, the third film thickness ratios for wafers W1 and W3 of Experimental Examples 1 and 3 were calculated based on the following formula (5). Third film thickness ratio = average film thickness in the transport direction area / average film thickness in the central area … (5) Then, a third influence evaluation value for evaluating the influence of the contact area between the contact portion and the leg portion in the conveying direction was calculated based on the following formula (6). Third influence evaluation value=third film thickness ratio on wafer W3 of experimental example 3 / Third film thickness ratio in wafer W1 of Experimental Example 1 … (6) The calculation results of equations (5) and (6) are shown in Table 4.

[0053] [Table 4]

[0054] As shown in Table 4, the third impact evaluation value was a value exceeding 1. Here, the contact area between one second contact portion 254 and the leg portion 212 of Experimental Example 3 adjacent to the radial outside of each transport direction region A4 during film formation was larger than the total value of the contact areas between the two first contact portions 233 and the leg portion 212 of Experimental Example 1. From this, it was confirmed that the contact area between the contact portion 223 and the leg portion 212 in the transport direction and the film thickness distribution of the oxide film have a correlation such that the larger the contact area of ​​the portion on the transport direction side of the tray body 22, the thicker the oxide film in the region adjacent to the portion on the transport direction side in the outer periphery of the wafer W becomes relative to the central portion. Note that the transport direction side portion of the tray body 22 on which the contact portion 223 is provided is a portion within a sector area that includes the center 221C of the recess 221, is symmetrical with respect to a reference line T2 parallel to the transport direction and the vertical direction, and has a central angle θ2 of 90°, as shown in FIG. 3(B). Also, the transport direction region A4 is a region within the sector area shown in FIG. 3(B).

[0055] The present inventors speculate that the reason for such a correlation is as follows. As described above, during the formation of an oxide film on the wafer W in any film-forming tray 2, the film-forming trays exist on both sides of the film-forming tray 2 in the transport direction, but there are no film-forming trays 2 on both sides of the transport width direction, so the temperature on both sides of the tray body 22 in the transport direction is considered to be higher than that on the transport width direction side. For this reason, it is considered that the heat on both sides of the tray body 22 in the transport direction is transferred to the placement part 211 of the support member 21 through the contact parts 223 and the legs 212 on both sides of the transport direction. It is also considered that the amount of heat transferred to the placement part 211 of the support member 21 in this way increases as the contact area between the contact parts 223 and the legs 212 increases. From these facts, it was estimated that the larger the contact area between the contact parts 223 and the legs 212, the higher the temperature on both sides of the transport direction of the wafer W and the thicker the oxide film on both sides of the transport direction becomes.

[0056] In addition, from the estimation results described above, it is considered that the smaller the contact area between the contact portion 223 of the tray body 22 on the transport direction side and the leg portion 212, the lower the temperature of the outer periphery of the wafer W on the transport direction side, and the thinner the oxide film on the transport direction side will be compared to the central portion. Furthermore, when the contact portion 223 is not provided at the portion on the transport direction side of the tray body 22, it is considered that heat on the transport direction side of the tray body 22 is not transferred to the placement portion 211 of the support member 21 as compared to the case where the contact portion 223 is provided. From this, it is considered that when the contact portion 223 is not provided at the portion on the transport direction side of the tray body 22, the oxide film in the region adjacent to the portion on the transport direction side of the outer periphery of the wafer W is thinner than the central portion as compared to the case where the contact portion 223 is provided. That is, it was confirmed that there is a correlation (hereinafter, sometimes referred to as a "third correlation") between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 and the ratio of the thickness of the oxide film at the region adjacent to the portion on the transport width direction side at the outer periphery to the thickness of the oxide film at the center of the wafer W. The third correlation can also be said to be a correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 and the thickness of the oxide film at the region adjacent to the portion on the transport direction side at the outer periphery of the wafer W.

[0057] <Summary> The present inventor has found that the configuration requirements of the groove portion 222 and the contact portion 223 of the tray body 22 of the film formation tray 2 and the film thickness distribution of the oxide film on the wafer W have the first to third correlations as described above. The inventor then found that an oxide film having a desired film thickness distribution can be formed on a wafer W by using a first tray body 22 to form a first oxide film on a first wafer W in a specified film forming apparatus 1, obtaining a correlation between at least one of the constituent elements of the groove portion 222 and the contact portion 223 and the film thickness distribution of the oxide film, obtaining a target film thickness distribution of the oxide film, and determining, based on the film thickness distribution of the first oxide film and the correlation, the at least one constituent element capable of forming an oxide film of the target film thickness distribution as an applicable requirement, and using a second tray body 22 that satisfies the applicable requirement to form a second oxide film on a second wafer W in the specified film forming apparatus 1, thereby completing the present invention.

[0058] [Embodiment] <Method of forming oxide film> Next, a method for forming an oxide film according to an embodiment of the present invention will be described. Fig. 5 is a flow chart showing a method for manufacturing a wafer. Fig. 6 is a flow chart showing an oxide film forming process. In this embodiment, as a wafer manufacturing method, a manufacturing method of an epitaxial wafer including a product wafer W as a second wafer made of silicon, an epitaxial layer provided on the surface of the product wafer W, and a back surface oxide film (LTO film) as a second oxide film provided on the surface of the product wafer W will be described.

[0059] As shown in FIG. 5, the wafer manufacturing method includes a pulling up step S1, a block processing step S2, a slicing step S3, a pretreatment step S4, a double-sided polishing step S5, an oxide film forming step S6, a single-sided finishing step S7, a first cleaning step S8, an epitaxial layer forming step S9, and a second cleaning step S10.

[0060] In the pulling step S1, a cylindrical silicon single crystal is pulled up from a silicon melt by the Czochralski method. In the block processing step S2, the outer periphery of the single crystal ingot is ground, notched according to the crystal orientation, and cut into a plurality of blocks using, for example, a band saw. In the slicing step S3, the block is sliced ​​into a plurality of product wafers W, each having a thickness of, for example, about 1 mm, using an inner diameter blade cutter or a wire saw. In the pre-processing step S4, chamfering is performed and rough polishing (lapping) is performed with, for example, an alumina abrasive so that both surfaces of the product wafer W are parallel. Then, after etching or the like is performed as necessary, a flattening process is performed to remove unevenness on the surface of the product wafer W. In the double-sided polishing step S5, a double-sided polishing machine is used to perform mirror finishing on the pre-treated product wafer W to increase the flatness.

[0061] The oxide film forming step S6 corresponds to the oxide film forming method of the present invention, and includes the oxide film forming condition determining method of the present invention. In the oxide film forming step S6, a back surface oxide film is formed on the back surface of the product wafer W. In the single-sided finishing step S7, the front surface (the surface on which the back surface oxide film is not formed) of the product wafer W obtained in the oxide film forming step S6 is polished. By carrying out the polishing process in the single-sided finishing step S7, scratches and damage on the front surface of the product wafer W can be removed and the surface roughness of the front surface can be adjusted. In the first cleaning step S8, the product wafer W obtained in the single-side finishing step S7 is cleaned with, for example, an alkaline solution. In the epitaxial layer formation step S9, an epitaxial layer is formed on the surface of the product wafer W. In the second cleaning step S10, the epitaxial wafer obtained in the epitaxial layer forming step S9 is cleaned with, for example, an alkaline solution.

[0062] Next, the oxide film forming step S6 will be described in detail. 6, the oxide film forming step S6 includes a tray body preparing step S61, a preliminary oxide film forming step S62, a correlation obtaining step S63, a target film thickness distribution obtaining step S64, a tray body configuration determining step S65, and a film forming step S66. The preliminary oxide film forming step S62, the correlation obtaining step S63, the target film thickness distribution obtaining step S64, and the tray body configuration determining step S65 constitute an oxide film forming condition determining method. Each of the steps S61 to S66 will be described below.

[0063] In the tray body preparation process S61, the worker prepares multiple types of tray bodies 22 that differ from each other in at least one constituent element (e.g., a combination of number, shape, and position) of the groove portions 222 and the contact portions 223, such as the tray bodies 23, 24, 25, and 26 of the above-mentioned experimental examples 1 to 4.

[0064] In the preliminary oxide film formation step S62, a predetermined film formation apparatus 1 forms a test oxide film as a first oxide film on a test wafer W as a first wafer by using a first film formation tray 2 having a first tray body 22 and a support member 21. A measuring device (not shown) measures the film thickness distribution of the test oxide film. A computer (not shown) acquires the film thickness distribution of the test oxide film based on, for example, an operation of an input unit (not shown) by an operator or from the measuring device. The constituent features of the groove portion 222 and the contact portion 223 in the first tray body 22 are not particularly limited, and may be, for example, the constituent features of the tray body 22 in the above-mentioned Experimental Example 1. The first tray body 22 may be selected from a plurality of types of tray bodies 22 prepared in the tray body preparation step S61, or may be a type of tray body 22 different from the tray body 22 prepared in the tray body preparation step S61.

[0065] In the correlation acquisition step S63, the computer acquires the correlation between at least one of the constituent elements of the groove portion 222 and the contact portion 223 and the film thickness distribution of the oxide film from, for example, a storage unit (not shown). The correlation includes at least one of the above-mentioned first to third correlations. The correlation may be obtained by an experiment or a simulation.

[0066] In the target film thickness distribution acquisition step S64, the computer acquires the target film thickness distribution of the oxide film based on, for example, an operation of the input unit by an operator.

[0067] In the tray body configuration determination step S65, the computer determines, as an applicable requirement, at least one of the configuration requirements of the groove portion 222 and the contact portion 223 that can form an oxide film with a target thickness distribution, based on the thickness distribution of the test oxide film and the correlation. For example, when a film thickness distribution in which the first film thickness ratio based on the above formula (1) is a predetermined value is the target film thickness distribution, and the first film thickness ratio in the test oxide film is larger than the predetermined value, based on the first correlation, it is determined that the application requirement for groove portion 222 capable of forming an oxide film with the target film thickness distribution is to make the width of groove portion 222 larger than that of groove portion 222 of first tray body 22. In addition, when the target film thickness distribution of the outer periphery is a uniform film thickness distribution and the thickness of the region of the outer periphery of the test oxide film on the transport width direction side is thicker than other regions of the outer periphery, based on the second correlation, it is determined that the application requirement for the contact portion 223 capable of forming an oxide film with the target film thickness distribution is to make the contact portion 223 provided in the portion on the transport width direction side longer than the contact portion 223 of the first tray body 22 and increase the contact area with the leg portion 212. Furthermore, when the target film thickness distribution of the outer periphery is a uniform film thickness distribution and the thickness of the region of the outer periphery of the test oxide film on the transport direction side is thinner than the other regions of the outer periphery, based on the third correlation, the application requirement of the contact portion 223 capable of forming an oxide film with the target film thickness distribution is determined to be that the contact area between the contact portion 223 provided at the portion on the transport direction side and the leg portion 212 is made larger than the contact area on the first tray body 22. At least one of increasing the length of the contact portion 223 and increasing the number of the contact portions 223 can be applied as a method for increasing the contact area.

[0068] In the film forming step S66, the worker selects a second tray body 22 that satisfies the application requirements from among the multiple types of tray bodies 22 prepared in the tray body preparation step S61. If there is no tray body 22 that satisfies the application requirements among the multiple types of tray bodies 22, the worker selects a tray body 22 that has configuration requirements closest to the application requirements as the second tray body 22. Note that selecting a tray body 22 that has configuration requirements closest to the application requirements corresponds to selecting a second tray body 22 that satisfies the application requirements in the present invention. The predetermined film forming apparatus 1 forms a back surface oxide film on the back surface of the product wafer W by using the second tray body 22 selected by the operator.

[0069] <Effects of the embodiment> The oxide film forming method includes the above-mentioned oxide film pre-forming step S62, correlation obtaining step S63, target film thickness distribution obtaining step S64, tray body configuration determining step S65, and film forming step S66. In this way, based on the correlation between at least one of the constituent elements of the groove portion 222 and the contact portion 223 and the film thickness distribution of the oxide film, and based on the film thickness distribution of the test oxide film, the at least one constituent element capable of forming an oxide film with the target film thickness distribution is determined as an applicable requirement, and by forming a back surface oxide film on the product wafer using the second tray body 22 that satisfies the applicable requirement, an oxide film with a desired film thickness distribution can be formed on the wafer W. Furthermore, by performing the oxide film forming method and using the second tray body 22 corresponding to the device characteristics of each of the multiple film forming apparatuses 1, the variation in film thickness distribution of the oxide film among the multiple film forming apparatuses 1 can be reduced. Furthermore, since an oxide film having a desired film thickness distribution can be formed, the yield of the wafers W can be improved, and it is possible to realize improvements in energy efficiency, production efficiency, and waste reduction.

[0070] The correlation acquired in the correlation acquisition step S63 includes a first correlation between the width of at least a portion of the groove portion 222 in the circumferential direction and the thickness of the oxide film in a region adjacent to the at least a portion in the outer periphery of the wafer W. Therefore, by using the second tray body 22 in which the width of at least a portion of the groove 222 in the circumferential direction is appropriately set, an oxide film having a desired film thickness distribution can be formed.

[0071] It is preferable that the correlation acquired in the correlation acquisition process S63 includes a first correlation between the width of at least a portion of the groove portion 222 in the circumferential direction and the thickness of the oxide film in a region adjacent to said at least a portion in the outer periphery of the wafer W. Therefore, by using the second tray body 22 in which the width of at least a portion of the groove 222 in the circumferential direction is appropriately set, an oxide film having a desired film thickness distribution can be formed.

[0072] The correlation acquired in the correlation acquisition process S63 includes a second correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport width direction side of the tray body 22, and the thickness of the oxide film in the region adjacent to the portion on the transport width direction side at the outer periphery of the wafer W. Therefore, by using a second tray body 22 in which the contact area between the contact portion 223 and the leg portion 212 in the transport width direction side of the tray body 22 is appropriately set, an oxide film having a desired film thickness distribution can be formed.

[0073] The correlation acquired in the correlation acquisition process S63 includes a third correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22, and the thickness of the oxide film in the region adjacent to the portion on the transport direction side at the outer periphery of the wafer W. Therefore, by using a second tray body 22 in which the contact area between the contact portion 223 and the leg portion 212 at the transport direction side of the tray body 22 is appropriately set, an oxide film having a desired film thickness distribution can be formed on the wafer W. In particular, if the correlations acquired in the correlation acquisition step S63 include all of the first to third correlations, the film thickness distribution can be controlled more finely by using the tray body 22 obtained based on the first to third correlations.

[0074] The method for forming an oxide film includes a tray body preparation step S61. Therefore, in the film forming process S66, an oxide film having a desired film thickness distribution can be formed by the simple method of simply selecting a second tray body 22 that meets the application requirements from the multiple types of tray bodies 22 prepared in the tray body preparation process S61.

[0075] [Variations] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and various improvements and design changes that do not deviate from the gist of the present invention are also included in the present invention.

[0076] For example, a part of the oxide film pre-forming step S62, the correlation obtaining step S63, the target film thickness distribution obtaining step S64, and the tray body configuration determining step S65 may be performed by an operator. Specifically, the operator may check the film thickness distribution of the test oxide film measured by a measuring device (oxide film pre-forming step S62), check the correlation displayed on the display unit of a computer or on a sheet-like medium such as paper (correlation obtaining step S63), check the target film thickness distribution of the oxide film based on the product specifications, etc. (target film thickness distribution obtaining step S64), and perform the tray body configuration determining step S65.

[0077] By attaching an attachment to the recess 221, it is possible to provide a groove portion 222 and a contact portion 223 having specified configuration requirements, and by selecting one type of attachment from multiple types of attachments, a second tray body 22 that meets the applicable requirements can be created.

[0078] In a plan view, the tray body 22 may be a rectangle whose long sides are parallel to the conveying direction, a square, a polygon other than a rectangle, a circle, or an ellipse. [Industrial Applicability]

[0079] According to the method for determining oxide film formation conditions, the method for forming an oxide film, and the method for manufacturing a wafer of the present invention, an oxide film having a desired film thickness distribution can be formed, which improves the yield of wafers W, improves energy efficiency, improves production efficiency, and reduces waste. The product of the present invention (epitaxial silicon wafer with LTO film (back surface oxide film)) is mainly used for logic devices. The present invention can contribute to high precision semiconductor devices, and in turn plays an important role in industrialization as a fundamental technology necessary for the development and improvement of advanced industrial products. The product of the present invention can be used, for example, in the control systems of automobiles, home appliances, medical equipment, etc., making it possible to realize high quality and high reliability products. [Explanation of symbols]

[0080] 1...film formation apparatus, 2...film formation tray, 21...support member, 211...placement portion, 212...leg portion, 22, 23, 24, 25, 26...tray body, 221...recess, 222, 232, 242, 252, 262...groove portion, 223...contact portion, 233, 243...first contact portion, 254...second contact portion, G1...raw material gas, W...wafer.

Claims

1. 1. A method for determining conditions for forming an oxide film on a wafer using a film forming apparatus, comprising: the film formation apparatus is configured to form the oxide film on the wafer by using a film formation tray including a support member for supporting an outer periphery of the wafer and a tray body for supporting the support member, and supplying a source gas onto the wafer while heating the film formation tray; the support member includes a ring-shaped mounting portion on which the wafer is placed and legs extending downward from the mounting portion; the tray body includes a cylindrical recess for accommodating the support member, and a plurality of grooves formed along an outer edge of a bottom surface of the recess, and is configured to support the legs of the support member by contact portions located between a pair of adjacent grooves; The method for determining conditions for forming an oxide film comprises the steps of: a pre-oxide film formation step of forming a first oxide film on the first wafer by using the first tray body; a correlation acquisition step of acquiring a correlation between at least one of the constituent features of the groove portion and the contact portion and a thickness distribution of the oxide film; a target thickness distribution acquisition step of acquiring a target thickness distribution of the oxide film; A method for determining conditions for forming an oxide film, comprising: a tray body configuration determination process for determining, as an applicable requirement, at least one configuration requirement capable of forming the oxide film having the target film thickness distribution based on the film thickness distribution of the first oxide film and the correlation.

2. 2. The method for determining conditions for forming an oxide film according to claim 1, A method for determining conditions for forming an oxide film, wherein the correlation includes a first correlation between the width of at least a portion of the groove in a circumferential direction and the thickness of the oxide film in a region adjacent to the at least a portion in the outer periphery of the wafer.

3. 2. The method for determining conditions for forming an oxide film according to claim 1, the film formation apparatus is configured to form the oxide film on the wafer supported by each film formation tray while arranging a plurality of the film formation trays, each of which includes the tray body, in a feed direction and transporting the plurality of film formation trays in the feed direction; A method for determining conditions for forming an oxide film, wherein the correlation includes a second correlation between the contact area of ​​the contact portion and the leg portion in a portion of the tray body on the transport width direction side perpendicular to the feed direction, and the thickness of the oxide film in a region adjacent to the portion on the transport width direction side in the outer periphery of the wafer.

4. 4. The method for determining conditions for forming an oxide film according to claim 3, The method for determining an oxide film forming condition, wherein the second correlation is a relationship in which the larger the contact area at the portion on the transport width direction side, the thinner the oxide film in the region adjacent to the portion on the transport width direction side.

5. 2. The method for determining conditions for forming an oxide film according to claim 1, the film formation apparatus is configured to form the oxide film on the wafer supported by each film formation tray while arranging a plurality of the film formation trays, each of which includes the tray body, in a feed direction and transporting the plurality of film formation trays in the feed direction; A method for determining conditions for forming an oxide film, wherein the correlation includes a third correlation between the contact area of ​​the contact portion and the leg portion at the portions of the tray body on the feed direction side and the opposite direction side relative to the feed direction, and the thickness of the oxide film in the region adjacent to the portions on the feed direction side and the opposite direction side at the outer periphery of the wafer.

6. 6. The method for determining conditions for forming an oxide film according to claim 5, The method for determining conditions for forming an oxide film, wherein the third correlation is such that the larger the contact area at the portions on the feed direction side and the opposite direction side, the thicker the oxide film in the regions adjacent to the portions on the feed direction side and the opposite direction side.

7. A step of performing the method for determining conditions for forming an oxide film according to any one of claims 1 to 6; and a film forming step of forming the second oxide film on the second wafer using the second tray body that satisfies the application requirements.

8. 8. The method for forming an oxide film according to claim 7, A tray body preparation step of preparing a plurality of types of the tray bodies each having at least one constituent feature different from each other is further included, The film forming process is a method for forming an oxide film, in which the second tray body is selected from the at least one constituent element corresponding to each of the multiple types of tray bodies, and the second oxide film is formed using the second tray body.

9. A method for manufacturing a wafer, comprising the step of forming an oxide film on the second wafer by the method for forming an oxide film according to claim 7.

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