JPH01204427A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an excellent semiconductor whose minimum machining size is 0.3mum or less, by manufacturing the semiconductor through steps wherein the semiconductor is in contact with at least supercritical gas. CONSTITUTION:A cleaning bath 1 is composed of a supercritical gas feeding system 2, an exhausting system 3 and a third component feeding system 4. Valves 21 and 41 in the feeding systems are switched in correspondence with purposes. A filter 5 is provided in the feeding system 2 so as to prevent the inflow of foreign material into the cleaning bath 1. A heater 6 serves the role for keeping the temperature of the gas that is supplied into the cleaning bath at a critical temperature or higher. A pressure regulating valve 32 in the exhausting system serves the role for keeping the pressure of the gas at a critical pressure or higher. A substrate 7 that is sent from each step is loaded in the cleaning bath 1. The substrate is brought into contact with the supercritical gas. Thus, the permeability of the supercritical gas into minute parts and the third component are selectively incorporated into the supercritical gas. All conceivable contaminations at preset in the minute parts are removed in this way, and each step is optimized. Thus a semiconductor having excellent quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor having a minimum processing dimension of 0.3 μm or less, and particularly to a semiconductor having a trench structure and having the same dimension or less.

[Conventional technology]

The degree of integration of semiconductors continues to increase year by year. For example, D RAN (Dynamic Random
AccessMemory) is used for large computers, communication equipment, and various OA (Office A+1tomat)
ion) devices and terminal devices. As systems become more sophisticated and more compact, the size of DRAMs is increasing at a rate of four times every three years. 256KDRA
Mass production of M began in 1983, and IM began in 1986.
Mass production of DRAM has begun. It is expected that 4MDRAM and beyond will also follow this trend. As the degree of integration increases, the minimum processing dimensions are 2μm, 1.2μm, and 0.8μm.
It becomes finer as m.

The cleaning necessary for manufacturing these semiconductors uses organic solvents, hydrofluoric acid,
Wet cleaning using ultrapure water is the mainstream.

The liquid has a high density and dissolves and removes various dirt components. Also, since the viscosity is high, fine particles adhering to the wafer are washed away. Furthermore, the liquids mix well with each other, and the liquid adhering to the wafer can be replaced with another liquid. Since the liquid has the above-mentioned properties, wet cleaning has been the mainstream until now.

[The problem that the invention attempts to solve]

In the future, miniaturization will occur as the degree of integration increases (minimum processing size is 0.
3 μm or less) and trench structuring, the surface tension of the liquid makes it impossible for the liquid to penetrate into minute parts, so there is a problem that wet cleaning cannot be used.

Semiconductors are manufactured by subjecting a silicon wafer to multiple processes such as cleaning, oxidation, thin film formation, and impurity diffusion.

The silicone surface is extremely hydrophobic and cannot be wetted by water-soluble liquids. Therefore, it is impossible for a water-soluble liquid (hydric acid, ultrapure water, etc.) to penetrate into a trench of the above dimensions covered with a silicon surface due to its surface tension (interfacial tension with silicon).

That is, it is difficult to clean the inside of the trench after forming the trench.

The inventors have conducted various studies regarding the cleaning of minute parts with minimum processing dimensions of 0.3 μm or less, which are difficult to handle with wet cleaning.

Although gas can penetrate into even the smallest places, it has almost no cleaning power. On the other hand, liquids have a cleaning power similar to that of ``double'', but cannot penetrate into minute areas.

The inventors discovered the following facts and arrived at the present invention.

(1) Supercritical gas is the cleanest solvent.

(2) Supercritical gas easily penetrates into pores of 0.3 μm or less and dissolves what is present in the pores.

An object of the present invention is to provide a semiconductor having a minimum processing dimension of 0.3 μm or less.

[Means to solve the problem]

The present invention is characterized in that it is manufactured through a process of contacting with at least supercritical gas, and has a minimum processing size of 0.3 μm.
It is a semiconductor with a diameter of m or less.

Figure 2 shows supercritical carbon dioxide gas (pressure 150 kg/ry
τ, temperature 45°C). The vertical axis shows pressure loss per m length. In the figure, the characteristics for water and carbon dioxide gas are also shown. The pressure loss of supercritical carbon dioxide is 10% of that of water and about three times that of carbon dioxide, so it can be handled in the same way as carbon dioxide. That is, it is possible to remove foreign substances present in the supercritical carbon dioxide gas using a Pub filter in the same way as in the air introduced into a clean room. The concentration of particles in the air inside a class 10 super clean room is 0.00036 particles/mQ of 0.1 μm or more, and particles in supercritical gas can be cleaned to the same degree. References showing the number of fine particles in chemicals currently used in the semiconductor manufacturing field: VLSI Ull 1-La Clean Technology Symposium Na 6, Proceedings, +986.3. As shown in page 220), compared to these, supercritical gas is an extremely clean 1' container.

FIG. 3 shows the result of contacting the synthetic resin with supercritical carbon dioxide gas and removing the liquid present in the resin pores.

The vertical axis is the value obtained by dividing the amount of liquid removed by the amount of test resin. The horizontal axis indicates the amount of supercritical carbon dioxide gas (value converted to standard state) supplied to the resin column. The test resin is styrene divinylbenzene,
Among various adsorption materials, it has the highest hydrophobicity. The diameters of the countless pores that exist inside the resin range from 80 to 2,000. In the figure, the densities of supercritical carbon dioxide are 0.41 and 0.6.
The removal characteristics in the case of 8 g/i are shown. - The dotted chain line indicates the liquid content calculated from the pore volume of the test resin. Although the removal rate varies depending on the supercritical carbon dioxide density, the amount of recovered liquid/the amount of resin in a saturated state almost matches the resin liquid content in any case. This indicates that almost all of the liquid present in the pores having a diameter of 80 to 2,000 pores was removed. In other words, supercritical carbon dioxide gas can easily (quickly) penetrate into pores of 0.3 μm or less and remove what is present there.

Activated carbon (pore size: 1 to 10 μm) is also a highly hydrophobic material, but in experiments in which activated carbon was brought into contact with supercritical carbon dioxide, almost all of the liquid containing activated carbon could be removed. .

〔Example〕

In the semiconductor manufacturing process, for example, in the case of a Si wafer (substrate), an oxide film (Si02) is formed on the surface of the substrate, resists 1-
Coating, exposing through a mask, developing and etching, removing resist 1 to form a pattern on the substrate, etching,
The process of ion implantation (diffusion) of boron, phosphorus, etc. is repeated many times to carve the necessary circuits into the substrate. Finally, AQ or the like is deposited, electrodes are attached, and a semiconductor is obtained by dicing and pancaging. In these steps, defects occur on the surface of the substrate or on the inner surface of the trench structure accompanying the formation of the upper pattern due to the presence of organic contamination or inorganic contamination, and the resulting semiconductor becomes unusable. Therefore, cleaning work is essential before each process. The main objective of the present invention is to provide a semiconductor from which these contaminants have been completely removed by bringing the substrate into contact with a supercritical gas in this step. FIG. 1 shows a specific example of the present invention applied to this cleaning process, and will be described with reference to one drawing. As shown in FIG. 1, the cleaning tank 1 is composed of a supercritical gas supply system 2, a discharge system 3, and a third component supply system 4, and the valves 21 and 41 in the supply systems are switched depending on the purpose of each. Furthermore, a filter 5 is provided in the supply system 2 to prevent foreign matter from entering the cleaning tank 1. The heater 6 plays the role of maintaining the gas supplied into the cleaning tank above the critical temperature, and the pressure regulating valve 31 in the discharge system plays the role of maintaining the gas above the critical pressure. Then, the substrates 7 transferred from each process are loaded into the cleaning tank 1 and brought into contact with supercritical gas.

The supercritical gas is CO2 (critical point: 73 atm).

31.1°C), N2 (critical point 33.5a jm, -1
47'C), CCQ F3 (critical point 39 atm, 28
．． A non-flammable and highly safe gas such as 8℃) is suitable.In particular, it dissolves organic substances well, so by maintaining an appropriate contact time, contaminants adhering to the substrate will be diffused into the gas and removed from the system. Can be discharged. In addition, organic solvents such as hydrocarbon solvents (hexane, benzene, toluene, etc.), halogenated hydrocarbon solvents (dichloromethane, Freon, etc.), alcohol solvents (ethanol, etc.), and ketone solvents (acetone, etc.) can be added to the supercritical gas. ) etc. are added as a third component from the supply system 4 in small quantities and brought into contact with the substrate, thereby increasing the affinity and removing a wide variety of organic contaminants. Inorganic contamination is also a major obstacle for semiconductors.

For example, a Si substrate is exposed to native Si○ in air.
If the oxidation process is performed as it is after a second film is generated, the density will be poor, resulting in an impure oxide film, and the diffusion of boron, phosphorus, etc. into the substrate in the subsequent ion implantation process will be inhibited, and the semiconductor Even the lives of people may be lost. In this case, as described above, acid/
Alkali, e.g. HCQ, + HF + HzO2+
These contaminants can be removed by mixing a small amount of N 2 Ha or the like with supercritical gas, bringing it into contact with the substrate, eluting it, and discharging the gas. As mentioned above, by increasing the permeability of the supercritical gas to the fine parts and selectively including the third component in the supercritical gas, we can remove all possible contamination of the fine parts and optimize each process. High quality semiconductors can be obtained.

Next, examples in which CO2 is used as the supercritical gas will be listed.

<Example 1> Ultrapure water was attached to the surface of a substrate (Si), and a pressure of 150a was applied.
tm, when brought into contact with supercritical carbon dioxide gas at a temperature of 50°C, ultrapure water can be completely removed, and organic substances dissolved in ultrapure water (total organic carbon content TOC = 4'6PPb) are deposited on the substrate. There was nothing left.

<Example 2> A substrate on which native S j 02 exists is used as Example 1.
Under these conditions, H (1, HF) was added to supercritical carbon dioxide gas and brought into contact, and after finally contacting with supercritical carbon dioxide gas alone, ultrapure water was dropped onto the surface of the substrate. This showed that native S 102 could be removed.

<Example 3> After implementing Examples 1 and 2, thermal oxidation was performed, and a 5iOz film was successfully formed on the substrate surface.

In addition, when a mixed gas of N2 and 02 in supercritical gas was brought into contact with the substrate, an SiO2 film (with a thickness of approximately 20 mm) was formed on the surface of the substrate.
0 people) were formed. The film was also of good quality as evaluated by measuring the breakdown voltage. From this, it is unaffected by CO2 even in environments with zero CO2.

This proves that an oxide film can be formed by containing a substance containing oxygen atoms.

<Example 4> A substrate (trench structure) coated with a positive type organic coating film, which had undergone pattern etching of approximately 10 μm, was subjected to the same treatment as described above. Peeling was removed without any damage. This shows that it is possible to remove and clean the photoresist in the pattern forming process.

<Example 5> Contact holes of 0.5 and 0.3 μm in Sj substrate,
After cutting a groove and treating a substrate simulating a trench structure in the same manner, the inside of the substrate was examined using a destructive analysis method. As a result, nothing other than Si could be detected, and a clean trench structure substrate was obtained. This shows the permeability of supercritical carbon dioxide gas into microstructures.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a high-quality semiconductor that has a high yield and suppresses the occurrence of defects.

[Brief explanation of the drawing]

Fig. 1 is a system diagram for bringing a semiconductor saw plate into contact with supercritical gas according to an embodiment of the present invention, Fig. 2 is a comparison diagram of the fluidity of supercritical carbon dioxide gas and other fluids, and Fig. 3 1 is a diagram showing the pores of a styrene divinylbenzene resin brought into contact with supercritical carbon dioxide gas according to the present invention. DESCRIPTION OF SYMBOLS 1... Cleaning tank, 2... Supercritical gas supply system, 3... Discharge system, 4... Third component supply system, 5... Filter, 6
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Grudge power + (N 47L3)

Claims (1)

[Scope of Claims] 1. A semiconductor device manufactured through at least a step of contacting with supercritical gas, and characterized in that the minimum processing dimension is smaller than 0.5 μm. 2. The semiconductor device according to claim 1, wherein the minimum processing dimension is 0.1 μm or more and less than 1.5 μm.