Base heater block with an asymmetric heating wire structure

Abstract

The present invention provides a pedestal heater block for a chemical vapor deposition machine, characterized in that a vacuum application structure is provided on the surface to fix the wafer by vacuum adsorption, and there are air supply holes for supplying temperature equalization gas to the back surface of the wafer and heating wires for heating the wafer. The heating wires are arranged such that the central portion of the heater block corresponding to the central portion of the wafer is greater than the peripheral portion outside it. Among them, for the convenience of setting, the arrangement of the heating wires can adopt an asymmetric type such as a cochlear shape instead of a left-right symmetric type. In the case of the asymmetric type, it can be set as a cartridge heater. According to the present invention, when a wafer or a substrate is placed on the pedestal heater block and a chemical vapor deposition process is performed, when a low pressure, such as a low pressure of 3 Torr or less, is applied to the back surface of the substrate and the vacuum adsorption force increases, by setting the heater at a density greater than that of the peripheral portion at the central portion of the heater block corresponding to the position where the wafer is likely to become low temperature, the temperature deviation of the entire wafer during the deposition process can be reduced compared with the prior art, and the thickness uniformity and homogeneity of the film deposited on the wafer can be improved.

Description

Technical Field

[0001] The present invention relates to a base heater block, and more particularly, to a base heater block having an asymmetric heating wire structure and having high temperature uniformity within the heater block. Background Art

[0002] Semiconductor devices are generally fabricated using various processes such as diffusion using heat or ion implantation, lamination of material layers, and patterning using photolithography, etc., to form semiconductor devices and circuits including the same on a semiconductor substrate or a wafer.

[0003] As a method for laminating material layers, physical lamination such as sputtering and chemical deposition can be used, and a chemical vapor deposition machine can be used as a semiconductor device manufacturing apparatus responsible for chemical deposition.

[0004] Chemical vapor deposition is a method for forming a material layer, in which a vaporized thin film raw material is injected into a process chamber through a carrier gas or a liquid delivery system (LDS), and chemical processes such as adsorption and decomposition are performed on a heated substrate to deposit a material thin film.

[0005] Important characteristics that the raw material compounds used in this chemical vapor deposition method should possess include high vapor pressure, liquid compounds, vaporization temperature and thermal stability during storage, easy handling, easy reaction with reactants during the process, simple deposition mechanism, and easy removal of by-products. When depositing and forming a material thin film by this chemical vapor deposition method, it is necessary to uniformly maintain process conditions such as deposition temperature over the entire substrate in order to form the thin film with a uniform thickness and composition.

[0006] Figure 1 A cross-sectional view showing the structure of a base heater block for placing a process wafer in an existing chemical vapor deposition machine is shown. As shown, it includes: a base 10 (base block) on the surface of which a substrate is placed (not shown) and deposition is performed by vacuum adsorption; a rear cover 20 coupled to the rear side of the base 10; an outer rod 40 serving as a medium for fixing the base 10 and the rear cover 20 to a chamber (not shown); an inner rod 30 for lifting and lowering the base 10 and the rear cover 20; a sheath heater 50 for heating the base 10; a vacuum tube 60 for fixing the substrate by vacuum adsorption; a gas supply pipe 70 for supplying argon, the argon being discharged to the back of the substrate to uniformly transfer the heat of the heater block to the substrate; and a temperature sensor tube 80 through which a temperature sensor passes to detect the temperature of the base 10.

[0007] However, an electric heating wire is formed inside the heater block. While transferring heat to the wafer, it is necessary to maintain a uniform temperature. However, depending on the arrangement of the electric heating wire, a temperature difference appears at different positions in the substrate, making it difficult to form a homogeneous and uniform-thickness deposition film by chemical vapor deposition.

[0008] Figure 2 FIG. is a top view showing the shape of the existing arrangement of the electric heating wire. In this structure, the arrangement of the electric heating wire is symmetric about a diameter of the circular heater block 110. Also, the electric heating wires 120 are relatively uniformly distributed in the peripheral part and the central part of the heater block.

[0009] Generally, when the electric heating wires are uniformly distributed in the central part and the peripheral part of the circular wafer, it may be expected that the heat transfer from the heater block to the wafer is also uniform and the temperature difference at different positions in the wafer is not large. However, in the actual structure, the temperature of the wafer in the central part of the wafer is lower, and the temperature difference between the high-temperature part and the low-temperature part is as high as 4 - 5 degrees Celsius.

[0010] This temperature difference may seem insignificant, but even the slight difference in the thickness of the deposition film caused by this temperature difference will have a huge impact on the semiconductor device or circuit as the final result of the process, because semiconductor devices are highly integrated and miniaturized, so it is necessary to minimize this difference as much as possible.

[0011] A detailed investigation of the temperature deviation phenomenon was carried out to solve the problems in the existing heater block. As a result, it was confirmed that when pressure is applied to the back surface of the wafer through a vacuum structure such as a vacuum hole formed in the heater block for vacuum adsorption and a groove 130 connected thereto in order to stably mount the wafer to the heater block, when the back surface air pressure is very low, about 3 torr, and the vacuum adsorption force increases, this temperature difference is very large, and the low-temperature part in a partial area of the central part is significantly lower than the peripheral part. SUMMARY OF THE INVENTION

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] An object of the present invention is to provide a pedestal heater block having a structure capable of reducing the temperature deviation of a wafer placed on a pedestal heater block of an existing chemical vapor deposition machine.

[0014] Another object of the present invention is to provide a pedestal heater block having an electric heating wire structure capable of reducing the temperature deviation at different positions in a wafer during the chemical vapor deposition process of the wafer.

[0015] TECHNICAL SOLUTION FOR SOLVING THE PROBLEM

[0016] To achieve the above object, the present invention is characterized in that in a base heater block for a chemical vapor deposition machine, a vacuum hole for fixing a wafer by vacuum adsorption is provided in the central part, a gas for temperature uniformity is supplied to the back surface of the wafer, and heating wires are arranged such that the setting density in the central part of the heater block is greater than that in the peripheral part outside it, wherein the central part of the heater block is a position corresponding to the central part of the wafer based on a position within 1 / 2 to 4 / 5 of the radius, preferably within 3 / 5 to 2 / 3.

[0017] In the present invention, for the convenience of setting, the arrangement of the heating wires can adopt an asymmetric form such as a cochlear shape instead of a left-right symmetric form. In the case of the asymmetric form, a cartridge heater can be set instead of a sheath heater.

[0018] In the present invention, preferably, the heater block body is made of aluminum or aluminum alloy having excellent thermal conductivity, and a coating film for increasing thermal conductivity is formed on the surface.

[0019] In the present invention, the groove formed on the surface of the heater block has a wider width and a shallower depth compared with the prior art to increase the pressing force when the back pressure applied to the back surface of the wafer during the process is maintained below 3 Torr. For example, the cross-section of the existing groove is a nearly square cross-section with a width of 1.2 mm to 1.9 mm and a depth of 1.2 mm to 1.9 mm, while the width of the groove of the present invention can be increased by about 1 - 1.5 times to 2.3 mm to 3.0 mm, and the depth can be increased by about 0.3 - 0.6 times to 0.5 mm to 1.0 mm, so that the overall shape has a width 2 - 6 times larger than the depth.

[0020] Effects of the Invention

[0021] According to the present invention, when a wafer or a substrate is placed on the base heater block and a chemical vapor deposition process is performed, when a low pressure, such as a low pressure below 3 Torr, is applied to the back surface of the substrate and the vacuum adsorption force increases, the flow of the gas for temperature uniformity for making the temperature of the entire surface of the substrate uniform is insufficient, resulting in a temperature deviation. In this case, heat can also be transferred more to the central part and less to the peripheral part by setting heaters at a greater setting density in the central part of the heater block corresponding to the position in the wafer where it is likely to become low temperature, so that the temperature deviation of the entire wafer during the deposition process can be reduced compared with the prior art, and the thickness uniformity and homogeneity of the film deposited on the wafer can be improved. Description of the Drawings

[0022] Figure 1 A side cross-sectional view showing the structure of an existing base heater block for a chemical vapor deposition machine.

[0023] Figure 2 To show a simplified top view of an example in which heating wires in a base heater block for a chemical vapor deposition machine are evenly arranged in a left - right symmetric manner

[0024] Figure 3 To conceptually and briefly show a structural concept diagram of a base heater block with heating wires in an asymmetric structure cartridge - type manner according to an embodiment of the present invention

[0025] Figure 4 To show a simplified top view of the shape in which the cartridge - type heating wires according to an embodiment of the present invention are arranged asymmetrically

[0026] Figure 5 According to the prior art and Figure 4 Thermographic images of a wafer when heat is transferred according to an embodiment, where different temperatures are shown in different colors for comparing the temperature distribution

[0027] Figure 6 To show a top view of a test wafer for measuring temperatures at different positions and each temperature - measuring position when the wafer temperature in a chemical vapor deposition machine is set to 300 degrees Celsius in the case of the existing heating - wire distribution and the heating - wire distribution according to an embodiment of the present invention

[0028] Figure 7 To show thermographic images of the temperature distribution at different positions in a test wafer according to several combinations of process - chamber pressure and back - side pressure when the wafer temperature in a chemical vapor deposition machine is set to 300 degrees Celsius in the case of the existing heating - wire distribution and the heating - wire distribution according to an embodiment of the present invention Detailed Description of the Invention

[0029] Hereinafter, the present invention will be described more specifically through embodiments of the present invention with reference to the accompanying drawings

[0030] Figure 3 To conceptually and briefly show a structural concept diagram of a base heater block with heating wires in an asymmetric structure cartridge - type manner according to an embodiment of the present invention Figure 4 To show a simplified top view of the shape in which the cartridge - type heating wires according to an embodiment of the present invention are arranged asymmetrically

[0031] In a general structure, the base heater block of the present invention has no significant difference from the structure shown in Figure 1 Referring to the accompanying drawings, the inner rod 240 part is coupled to the heater block 210 or the center of the base. The heating wire 220 of the cartridge - type heater extends from the inside of the inner rod 240 and is arranged in the heater block 210. And in the inner rod 240, there are provided: a wafer - holding tube 260 for applying a vacuum for holding a wafer (substrate), an argon - supply tube 250 arranged in a way of being connected from the outside, and a temperature - sensor tube 270

[0032] In the present invention, the general structure of the base heater block is the same as that of the existing heater block in many aspects. The difference lies in that the arrangement shape of the heating wire disposed in the heater block is changed from the existing Figure 2 symmetric left - right shape shown and uniformly distributed in the peripheral part and the central part to an asymmetric shape such as a cochlear shape like a snail shell or a vortex shape.

[0033] Moreover, in the present invention, the current input end and the output end of the existing heating wire are respectively formed on both sides and the wire is in a single - layer sheath type, which is changed to a cartridge type in which the current input end and the output end are stacked and formed only on one side of the heating wire and the wire is in a double - layer stacked form. This cartridge type is convenient for designing the setting shape when the heating wire 220 is arranged asymmetrically, so it is more advantageously used in this case.

[0034] The cochlear shape has a shape similar to concentric circles, but the difference is that all parts of the heating wire 220 are interconnected and are composed of a single wire that rotates from the center to the outside in a direction similar to the circumferential direction and winds around multiple times. In such a cochlear - shaped heating wire, a specified distance can be provided between the inner heating wire part and the adjacent outer heating wire part, and the connection to the external power supply can be achieved through the end of the heating wire located in the central part of the heater block.

[0035] In the heater block 210 that is circular in a top view, the circle that connects the straight line extending radially from the center to the periphery and the end of the peripheral part of the straight line is a groove 230 formed on the surface of the heater block 210 for placing the wafer. The end of the central part of the radially - extending straight line can be connected to the central vacuum hole for vacuum adsorption. Therefore, the negative pressure for vacuum - adsorbing the wafer can be applied to the entire back surface of the wafer through the groove 230.

[0036] Among them, the width and depth of the groove formed on the surface of the heater block can be increased or decreased according to the position or area to correct the temperature uniformity according to the back pressure. It can have a wider width and a shallower depth compared with the prior art to increase the pressing force when the back pressure applied to the back surface of the wafer during the process is maintained below 3 Torr. For example, the cross - section of the existing groove is close to a square with a width of 1.2 mm to 1.9 mm and a depth of 1.2 mm to 1.9 mm, while the width of the groove of the present invention can be increased by about 1 - 1.5 times to 2.3 mm to 3.0 mm, and the depth can be increased by about 0.3 - 0.6 times to 0.5 mm to 1.0 mm, making the overall shape wider than deep.

[0037] On the surface of the heater block 210, in addition to the groove 230, air supply holes are provided at multiple positions, and the air supply holes are distributed on the entire surface. The gas supplied from the air supply holes mainly uses inert gases such as argon or helium.

[0038] Although a large portion of heat is transferred to the wafer placed on the heater block through direct conduction, since the heating wire is a wire and the surface of the heater block is a surface, the heating wire cannot be completely evenly distributed on the entire surface of the heater block. Even if the heater block is made of materials such as aluminum with excellent thermal conductivity, temperature deviations will occur at different locations.

[0039] The gas from the gas supply holes contacts and flows in the space between the heater block surface and the back of the wafer to form an airflow, which takes away heat from some high-temperature parts and supplies heat to some low-temperature parts during the gas flow, and is discharged through the grooves and vacuum holes.

[0040] The size of the back pressure can be adjusted throughout the entire process. If the back pressure becomes very low during the process, such as below 3 Torr and the vacuum adsorption force increases, the wafer will be partially deformed, and the center part with the vacuum hole will be closer to the surface of the heater block, making it difficult for the gas to be discharged from the gas supply hole in the center and flow smoothly between the heater block and the substrate, making it difficult to serve as a temperature uniformization gas.

[0041] As a result, a portion of the wafer temperature remains lower than other portions in the center portion, and therefore, in the present invention, the arrangement density of the heating wires in the center portion of the heater block is made greater than that in the surrounding portion to eliminate such temperature imbalance. That is, even if the gas flow is not smooth and the heat supply through the gas is reduced, the overall temperature deviation can be reduced by concentrating the heating wires in the center portion, thereby transferring more heat through conduction.

[0042] In the present invention, taking a point ranging from 2 / 3 to 3 / 5 from the center of the entire circular heater block as a reference, the cochlear-shaped heating wire is mainly distributed in the inner central portion, and in the outer peripheral portion, a portion of the end of one side of the asymmetrically distributed heating wire extends toward the peripheral portion, but this portion does not cause much impact as a whole.

[0043] therefore, Figure 4 The shape of the heating wire 220 of the embodiment is as follows: when the center portion is defined as a point ranging from 2 / 3 to 3 / 5 of the radius from the center of the circular heater block, it is arranged in a cochlear shape only in the center portion and is almost not distributed outside.

[0044] Although there may be some differences according to conditions, the radius of the wafer placed on the heater block is almost the same as or about 10% smaller than that of the heater block. Therefore, when the dense area of the heating wire is reduced to the position range from the center of the heater block to about 1 / 2 of the radius, the temperature range of the peripheral area is lower than that of the central area. Therefore, when setting the dense area of the heating wire, a point at least more than 1 / 2 of the radius is used as a reference to increase the setting density of the inner heating wire. On the contrary, when defining the dense area of the heating wire inside based on a point more than 4 / 5 of the radius from the center, the temperature of the central part is still higher than that of the peripheral part, and the temperature deviation may not be sufficiently reduced.

[0045] Of course, according to the situation, differently from this embodiment, a part of the heating wire can also be arranged on the outside, but the setting density on the outside is less than that of the central part. It can be seen that this distribution of the heating wire is different from Figure 2 the existing symmetric distribution of the heating wire shown. In the distribution example of the prior art, the heating wire is relatively evenly distributed when observed in the radial direction, and the heating wire is also arranged around the peripheral corners of the heater block.

[0046] For this structure, the heating wire can be made in the following way. First, the wires are stacked to form a simple linear cartridge type, and the simple linear cartridge type heating wire is deformed and inserted into the cochlear-shaped heating wire setting groove located at the base of the heater block and fixed to manufacture the cochlear-shaped heating wire. The terminals of the heating wire are bent and taken out to be connected to the rear rod of the heater block, and the rear cover is assembled to the rear side of the base. At this time, the bent terminals of the heating wire can pass through the through holes of the rear cover and be connected to the outside power supply through the center of the rear rod.

[0047] Alternatively, a groove is provided in a separate flat clamp, such as the shape of the cochlear-shaped heating wire setting groove located at the base of the heater block. The simple linear heating wire is inserted and deformed to form a cochlear shape, and the entire cochlear-shaped heating wire formed in this way is directly inserted into the cochlear-shaped heating wire setting groove located at the base to be combined. Similarly to the previous example, this structure is realized by using the method of combining the rear cover and the base.

[0048] Figure 5 is based on the existing Figure 2 example shown and the Figure 4 embodiment shown in the present invention. It is a contrast diagram of the temperature distribution when transferring heat to the wafer, where different temperatures are shown in different colors for comparing the temperature distribution. The upper part in the drawing shows the situation of the present invention, and the lower part shows the situation of the prior art.

[0049] In the case of the prior art, it can be seen that there is a part with a lower temperature presented as an oval elongated in the up and down direction slightly below the center of the wafer in the picture, and there are parts with higher temperatures around the upper left and right of the wafer.

[0050] In the case of using a heater block identical to the embodiment shown in Figure 4 a temperature-lower portion still appears slightly downward from the center of the wafer, but this time it presents as an oval elongated in the left-right direction, and no significantly higher-temperature portions appear in the upper left and right peripheral portions of the wafer.

[0051] Hereinafter, these results will be explained in more detail by comparison data with the prior art.

[0052] First, in a chemical vapor deposition machine named Green PD 12, a test wafer is placed on a heater block with a sheathed heating wire having a symmetric heating wire distribution as shown in Figure 2 and a heater block with a cartridge heating wire having a cochlear-shaped asymmetric heating wire distribution as shown in Figure 4 The temperature is set to 300 degrees Celsius, the process chamber pressure can be 10 / 40 torr, and the back pressure applied to the back of the test wafer can be 3 / 5 / 20 torr. Experiments are conducted using this equipment to compare the effects.

[0053] First, under the existing pressure conditions with a severe temperature deviation, that is, when the chamber pressure is 10 torr and the back pressure is 3 torr, the temperature is measured at each position from TC1 to TC17 of the test wafer as shown in Figure 6 The raw data obtained is shown in Table 1.

[0054] Table 1

[0055]

[0056] The results are sorted out to obtain Table 2.

[0057] Table 2

[0058]

[0059] Referring to Table 2, in the case of a heater block with the existing heating wire distribution, when the temperature of the chemical vapor deposition machine is set to 300 degrees Celsius, the highest temperature of 296.2 degrees Celsius is recorded in the upper right side according to the wafer position, the temperature around it is generally high, the temperature of the peripheral portion is generally high, and the lowest temperatures of 291.4 are recorded at the center portion TC9 and the center lower portion TC10. The temperature of the center portion is generally low. The temperature deviation reaches 4.8 degrees Celsius, the average temperature is 293.8, and the uniformity is 0.81%.

[0060] In the case of a heater block with the heating wire distribution of the embodiment of the present invention, under the condition that the temperature of the same chemical vapor deposition machine is set to 300 degrees Celsius, according to the wafer position, the highest temperature of 294.5 degrees Celsius is recorded on the left side. The temperature around it is generally high, and the temperature of the surrounding part is generally relatively high. The lowest temperature of 292.3 is recorded at the TC13 part in the lower right center, and the temperature of the central part is generally slightly lower. However, compared with the prior art, the temperature of the higher temperature part decreases by about 1.7 degrees Celsius, the temperature of the lower temperature part increases by about 0.9 degrees Celsius, the temperature deviation decreases by 2.6 degrees Celsius, and the average temperature is 293.4 without significant change, and the uniformity drops to 0.37%.

[0061] Generally speaking, the temperature of the previously higher temperature part has decreased a lot, and the temperature of the lower temperature part has increased slightly. Therefore, the temperature deviation has been greatly reduced. Of course, as the temperature deviation decreases, the thickness deviation of the deposition material at different positions in the wafer decreases. Therefore, the defective rate can be reduced and the yield can be improved.

[0062] Table 3 below expands the results of Table 2, obtains and arranges the original data of the temperature at different positions in the wafer under different process chamber pressures and back pressures, and the obtained results can be compared. That is, on the basis of the combination of a process chamber pressure of 10 Torr and a back pressure of 3 Torr (CASE1), as other pressure combinations, the results in the cases of a process chamber pressure of 10 Torr and a back pressure of 5 Torr (CASE2), and a process chamber pressure of 40 Torr and a back pressure of 20 Torr (CASE3) are also shown for comparison.

[0063] Table 3

[0064]

[0065] Referring to Table 3, it can be seen that compared with the embodiment in which the heating wire distribution is changed to an asymmetric cochlear shape, in the prior art, the higher the back pressure and the lower the vacuum adsorption degree, the overall temperature level of the wafer is closer to the set temperature of 300 degrees Celsius, and the temperature deviation is not large. In the case of applying the heater block with the structure of the present invention that changes the shape of the heating wire, the effect of improving the temperature deviation is shown, but the lower the back pressure, the greater the effect of eliminating the temperature deviation.

[0066] Figure 7A wafer thermal distribution photo showing the experimental results related to Table 3, where the upper side shows the case of a back pressure of 3 Torr, the middle shows the case of a back pressure of 5 Torr, and the lower side shows the case of a face pressure of 20 Torr. Overall, the left side is the case of the prior art and the right side is the case of the embodiment of the present invention. Overall, it shows a thermal distribution shape consistent with Table 3. That is, the lower the back pressure and the higher the vacuum adsorption force of the heater block on the wafer, the more obvious the temperature deviation, which indicates that there is an effect of improving the temperature deviation when the heater block of the present invention is applied.

[0067] As described above, the present invention has been described through limited embodiments, but this is only an exemplary description for helping to understand the present invention, and the present invention is not limited to these specific embodiments.

[0068] Therefore, those skilled in the art to which the present invention pertains can make various modifications or application examples based on the present invention, and these modifications or application examples naturally fall within the scope of the appended claims.

Claims

1. A pedestal heater block with an asymmetric heating wire structure, which is a pedestal heater block for a chemical vapor deposition machine, having a vacuum application structure on its surface to fix a wafer by vacuum adsorption, having an air supply hole for supplying a temperature equalizing gas to the back surface of the wafer and a heating wire for heating the wafer. It is characterized in that the back pressure applied to the back surface of the wafer by the vacuum application structure and the air supply hole is set to a low pressure of 3 Torr or less, the heater block is made of aluminum or an aluminum alloy, and the heating wire is arranged such that the setting density is greater at the central portion of the heater block than at the peripheral portion on its outer side; the current input end and the output end of the heating wire are stacked and formed only on one side of the heating wire and the wire is of a cartridge type with a double-layer stack; the terminal of the heating wire is connected to the rear rod of the heater block, the terminal of the bent heating wire passes through the through hole of the rear cover, and is connected to an external power supply through the center of its rear rod, and the heating wire is connected to the external power supply through the end of the heating wire located at the central portion of the heater block.

2. The pedestal heater block with an asymmetric heating wire structure according to claim 1, It is characterized in that the width of the groove formed on the surface of the heater block is in the range of 2.3 mm to 3.0 mm, and the depth is in the range of 0.5 mm to 1.0 mm, and the width is 2 - 6 times larger than the depth, so as to increase the pressing force when the back pressure applied to the back surface of the wafer during the process is maintained at 3 Torr or less.

3. The pedestal heater block with an asymmetric heating wire structure according to claim 1, It is characterized in that the central portion of the heater block is set based on a point within the range from the center to 3 / 5 to 2 / 3 of the radius of the circular heater block, and its outer side is the peripheral portion.

4. The pedestal heater block with an asymmetric heating wire structure according to claim 1 or 3, It is characterized in that the heating wire is in an asymmetric cochlear shape and is only distributed within the central portion.

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