TWI663131B - Surface treatment method of quartz vessel for diffusion process - Google Patents

Abstract

A surface treatment method for a quartz vessel for a diffusion process includes the following steps: a fire polishing step: the quartz vessel is subjected to a fire polishing to make the surface state consistent; an annealing step: eliminating stress in the quartz vessel; a masking step: masking a part that does not require sandblasting Sandblasting step: sandblasting the quartz vessel to form a roughened surface of the unshielded part; removing the shelter step: removing the shelter from the quartz vessel; the first cleaning step: washing the quartz vessel with a detergent; a chemical etching step : The surface of the quartz vessel is chemically etched; the second cleaning step: the quartz vessel is washed with pure water, thereby making the surface of the quartz vessel more uniform and smooth through the above steps, and increasing the surface area of the quartz vessel It has a good combination with the deposited layer, reduces the generation of particles in the process, improves the yield of the production wafer, and extends the life of the quartz vessel.

Description

Surface treatment method of quartz vessel for diffusion process

The present invention relates to a surface treatment method of a quartz vessel, and particularly to a surface treatment method of a quartz vessel for a diffusion process.

In the integrated circuit manufacturing process, a thermal diffusion furnace is often used to make P-type diffusion regions and N-type diffusion regions required for semiconductor devices, or a chemical vapor deposition method is used to deposit various materials required, such as by applying Silane is heated and dissociated to deposit the required polycrystalline silicon layer. Please refer to FIG. 1, which is a schematic diagram of the use of a conventional vertical thermal diffusion furnace. The conventional thermal diffusion furnace includes a reaction tube 1, which is provided with a plurality of heaters 2 on the outer side, and the inside of the reaction tube 1. A vertical quartz boat 3 is provided. The vertical quartz boat 3 is provided with a plurality of wafers 4 arranged side by side in a horizontal direction. The thermal diffusion furnace is connected with a plurality of gas-releasing reaction vessels 5. The reaction vessels 5 are supplied. Various processing gases are used to form a film on the surfaces of the wafers 4, and since the thermal diffusion furnace is often at a high temperature for the diffusion of various dopants, the temperature of the entire reaction tube 1 and the wafers 4 The temperatures to which they are subjected are comparable, so that in addition to being deposited on the wafers 4, the products of the reaction will also adhere to the inner wall surface of the reaction tube 1.

The surface treatment of the conventional reaction tube is mostly made of quartz after fire polishing. Please refer to Figure 2 for a sectional view of the conventional quartz surface processed by fire polishing. The flame polishing uses a flame (oxygen flame). The quartz surface is directly heated, and its surface is melted to form a transparent state without deforming. However, due to the long-term chemical vapor deposition method, a layer of deposited polycrystalline silicon is formed on the surface of the reaction tube. When the polycrystalline silicon layer accumulates, At a certain thickness, due to the smooth surface of the reaction tube after the fire polishing treatment, insufficient adhesion, and the stress on the surface of the polycrystalline silicon layer, it is easy to deposit a thicker part on the top of the reaction tube or a turning point on the surface of the reaction tube. Cracks or particles are formed. When the particles are peeled off, the wafers are contaminated, which greatly affects the yield of the wafers. The more serious case is that the polycrystalline silicon layer adheres to the peripheral wall of the reaction tube. The wall of the reaction tube sticks up, causing the wall of the reaction tube to peel off, making the surface of the reaction tube uneven and unusable, causing the reaction tube to be scrapped early.

The surface treatment of the conventional reaction tube also has a sandblasting treatment method. Please refer to Figure 3, which is a cross-sectional view of the conventional quartz surface processing by sandblasting. Quartz produces a rough surface, and the unevenness formed by the sandblasted quartz surface can be used to adsorb and keep the deposits attached. However, due to the complex shape of quartz products used in semiconductor production, during the blasting process, some surfaces cannot be directly contacted due to sand particles, so the strength, wind speed and distance of the spray are difficult to control. The roughness is not uniform, resulting in uneven roughness of the sandblasted surface, and the rough unevenness is too sharp, which makes the deposited layer easier to fracture and peel at the peaks, thereby forming particles and affecting the yield of the wafer.

The surface treatment of the conventional reaction tube also has a chemical processing method. Please refer to Figure 3, which is a cross-sectional view of the conventional chemical processing of the quartz surface. The chemical processing is pickling the quartz surface, such as hydrofluoric acid. The mixed solution of phosphoric acid and nitric acid is used for pickling to roughen the quartz surface and can be used to adsorb and keep the deposits attached. However, because the roughness of the inner wall surface of the quartz product is not consistent at the beginning, the roughness of the surface after chemical pickling is uneven, and some unevenness is too smooth, which makes the deposited layer easy to peel off at the smooth place, which affects the quality of the wafer. rate.

In addition, in the conventional semiconductor production process, usually in the same thermal diffusion furnace, the thickness and quality of film growth on all wafer surfaces must be consistent as much as possible, that is, the treatment of diffusion to the surface of each wafer in the thermal diffusion furnace is required. The gas is evenly distributed. However, if there are many wafers placed in the thermal diffusion furnace, the length of the inlet pipe of the processing gas in the thermal diffusion furnace must be relatively long, making the flow of the processing gas into the thermal diffusion furnace difficult. Keeping the same, so that the distribution of the processing gas on the surface of the wafer on the quartz boat is uneven, which makes the film thicknesses inconsistent between the wafers. Generally, the film thicknesses of the wafers on the top and bottom of the quartz boat Thicker wafers in the middle. Therefore, after observing the above-mentioned shortcomings, the inventor of the present case believes that it is necessary to improve the bonding strength between the quartz surface and the deposited layer, and to improve the uniformity of the film thickness between wafers, and the invention has been born.

The main object of the present invention is to provide a surface treatment method for a quartz vessel for a diffusion process, which can improve the bonding strength of the surface of the quartz vessel and the deposition layer, and increase the surface area thereof, thereby improving the yield of the wafer, and achieving Improve the uniformity of film thickness between wafers.

In order to achieve the above object, the surface treatment method of the quartz vessel for the diffusion process provided by the present invention comprises the following steps: a fire polishing step: the quartz vessel is fire polished to make the surface state uniform; the annealing step: The quartz vessel is gradually cooled after heating to eliminate the internal stress of the quartz vessel, so that the quartz vessel does not break naturally; the masking step: using several shields to partially shield the non-reactive surface of the diffusion process of the quartz vessel; sandblasting step : Sandblast the quartz vessel to make the unshielded part of the surface of the quartz vessel a roughened surface; step of removing the obstructions: remove the obstructions covering the surface of the quartz vessel; the first cleaning step: The quartz vessel is cleaned with a detergent; a chemical etching step: the surface of the quartz vessel is chemically etched to make the roughened surface more uniform and smooth; the second cleaning step: the quartz vessel is washed with pure water.

The surface treatment method of the quartz vessel used in the diffusion process of the present invention is to first make the state of the surface of the quartz vessel consistent through a fire polishing step, so as to facilitate subsequent processing, and then to roughen the surface of the unshielded part through the sandblasting step. Finally, the chemical etching step is used to make the roughened surface more uniform and smooth, so that the surface of the quartz vessel can be tightly and firmly combined with the deposited layer to improve the yield of the production wafer. In addition, since the roughened surface mainly It is formed on the reaction surface of the quartz vessel. Therefore, in the process of forming a thin film, the surface can absorb more processing gas, so that the concentration of the gas absorbed by the wafer set on the quartz vessel is more consistent, and the wafer can be improved. Uniformity of film thickness.

Please refer to FIG. 5, which is a flow block diagram of a preferred embodiment of the present invention, which discloses a surface treatment method of a quartz vessel for a diffusion process, which includes the following steps:

Fire polishing step: The quartz vessel is fire polished to make the surface state uniform.

Annealing step: After the quartz vessel is heated, it is gradually cooled to eliminate the internal stress of the quartz vessel, so that the quartz vessel does not break naturally.

Masking step: Partially mask the non-reactive surface of the quartz vessel diffusion process with several masking objects, and these masking objects are mainly set on the non-reactive surface of the quartz vessel diffusion process.

Sandblasting step: sandblast the quartz vessel to form a roughened surface on the unshielded part of the quartz vessel. The roughened surface has several sharp peaks, and because the shields mainly cover the surface of the quartz vessel The middle section thus makes the top and bottom of the quartz vessel have a roughened surface with a larger area.

Step of removing shielding: removing the shielding covering the surface of the quartz vessel.

The first cleaning step: the quartzware is cleaned with a cleaning agent, so that the fragile parts of the roughened surface can be removed by cleaning first, and the particles on the surface of the quartzware can be removed.

Chemical etching step: chemically etch the surface of the quartz vessel to make the roughened surface more uniform and smooth, and to make the peaks of the roughened surface more arc-shaped, as shown in FIG. 6, in this embodiment, it is used The surface of the quartz vessel is etched with an acidic chemical solution, and the acidic chemical solution is a mixed acid solution such as phosphoric acid (H3PO4), dimethylsulfine (DMSO), and the like.

The second cleaning step: washing the quartz vessel with pure water, so that the chemical solution on the surface of the quartz vessel can be removed by washing with pure water.

In order to further understand the structural features of the present invention, the use of technical means, and the expected effects, the manner of use of the present invention is described. It is believed that the deeper and specific understanding of the present invention can be obtained as follows:

The surface treatment method of the quartz vessel used in the diffusion process provided by the present invention is to first make the state of the surface of the quartz vessel consistent through the fire polishing step to facilitate subsequent processing, and then, through the masking step, to use several masking objects Partially mask the non-reactive surface of the quartz vessel in the non-diffusion process, and then roughen the unshielded part of the surface of the quartz vessel through a sandblasting step, and because the roughened surface is mainly formed on the quartz vessel in the diffusion process The reaction surface can increase the roughness and surface area of the quartz vessel. Next, the roughened surface particles are removed through the first cleaning step, and then the chemical etching step is used to make the roughened surface more uniform and smooth. The peaks of the roughened surface are more arc-shaped, and the chemical solution is cleaned and removed through the second cleaning step. As a result, the surface roughness of the quartz vessel is relatively uniform, and the surface area of the quartz vessel is increased. The deposits are tightly and firmly bonded, reducing the generation of particles during the process, The shortcomings of peaks and cracks formed by the method, and the disadvantages of uneven surface and excessively smooth part of the surface formed by the conventional chemical method, can increase the service life of the quartz vessel, and improve the yield of the production wafer, and make the The concentration of the gas adsorbed by the wafer set on the quartz vessel is relatively consistent, and the uniformity of the film thickness between the wafers can be improved.

Hereby, the features of the present invention and the expected effects that can be achieved are stated as follows:

1. The surface treatment method of the quartz vessel for the diffusion process of the present invention is to first make the state of the surface of the quartz vessel consistent through a fire polishing step to facilitate subsequent processing, and then to roughen the surface of the unshielded part through the sandblasting step. The surface is roughened. Next, the roughened surface particles are removed through the first cleaning step, and finally, the roughened surface is made more uniform and smooth through the chemical etching step. Thus, due to the roughness of the surface of the quartz vessel, It is more uniform and smooth, and increases the surface area of the quartz vessel, and can be tightly and firmly combined with the deposition layer, reducing the generation of particles during the process. Not only the shortcomings of the peaks and cracks formed by the sandblasting method, but also the conventional chemical method The disadvantages of uneven surface and excessively smooth surface are that it can improve the yield of production wafers and extend the life of the quartz vessel.

2. The surface treatment method of the quartz vessel used in the diffusion process of the present invention, since the roughened surface is mainly formed on the reaction surface of the diffusion process of the quartz vessel, increasing the surface area of the reaction surface of the quartz vessel, so in the process of forming a thin film As a result, more processing gas is adsorbed on the surface of the quartz vessel, so that the concentration of the gas adsorbed by the wafer set on the quartz vessel is more consistent, and the uniformity of film thickness between wafers can be improved.

In summary, the present invention has excellent progress and practicality among similar products. At the same time, it has traversed domestic and foreign technical data on such structures. It has not been found in the literature that the same structure exists first. Therefore, The present invention already has the elements of an invention patent, and the application is filed according to law.

However, the above is only one of the preferred feasible embodiments of the present invention. Therefore, any equivalent structural changes made by applying the description of the present invention and the scope of patent application should be included in the patent scope of the present invention.

[Habitant]

1‧‧‧ reaction tube

2‧‧‧ heater

3‧‧‧ vertical quartz boat

4‧‧‧ wafer

5‧‧‧ reaction container

Figure 1 is a schematic diagram of the use of a conventional vertical thermal diffusion furnace. Fig. 2 is a cross-sectional view of a conventionally processed quartz surface by fire polishing. Figure 3 is a cross-sectional view of a conventional sandblasted quartz surface. FIG. 4 is a cross-sectional view of a conventionally processed quartz surface. FIG. 5 is a flow block diagram of a preferred embodiment of the present invention. Figure 6 is a cross-sectional view of the surface of a quartz vessel formed through the steps of the present invention.

Claims (2)

A surface treatment method for a quartz vessel used in a diffusion process includes the following steps: a fire polishing step: the quartz vessel is fire polished to make the surface state consistent; an annealing step: the quartz vessel is heated and gradually cooled, Eliminate the internal stress of the quartz vessel so that the quartz vessel does not break naturally; the masking step: partially shield the non-reactive surface of the diffusion process of the quartz vessel with several shields; the sandblasting step: sandblast the quartz vessel so that The unshielded part of the surface of the quartz vessel forms a roughened surface; the step of removing the shields: removing the shields covering the surface of the quartz vessel; the first cleaning step: washing the quartz vessel with a detergent; Chemical etching step: The surface of the quartz vessel is chemically etched with an acidic chemical solution to make the roughened surface round and not sharp. The acidic chemical solution is phosphoric acid (H3PO4), dimethyl sulfoxide (DMSO) And other mixed solutions; the second washing step: washing the quartz vessel with pure water. According to the surface treatment method of the quartz vessel for the diffusion process according to item 1 of the scope of the patent application, in the masking step, the shielding objects are mainly disposed on the non-reactive surface of the quartz vessel.