JPS6057218B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement in a method for manufacturing a semiconductor device.

Conventionally, in the manufacture of semiconductor devices, there have been processes such as partial removal of silicon oxide films for selective diffusion and electrode extraction, partial removal of silicon for mesa etching, and even partial removal of metal vapor deposition films for interconnections. Photo-etching has been applied for removal. In this process, a photosensitive resin is first applied to the wafer, then heat treatment is performed, and then mask alignment is performed.

This mask alignment is used to set the parts of the photosensitive resin that will later be exposed to light and the parts that will not be exposed to light. After completing the above mask alignment, exposure, development, and heat treatment (post-bake)
After going through the process, it is inspected. The food then proceeds to the etching process, the removal process of the remaining photosensitive resin, and the subsequent processes such as oxidation and diffusion. By the way, so-called negative resists and positive resists are known as photosensitive resins, and a condensate of naphthoquinone-1;2 diamide sulfonyl chloride and novolak resin is known as a positive resist.

When this resist is exposed to light, the naphthoquinone-1;2 diamide group releases nitrogen under ultraviolet rays, becomes a ketene group, and further becomes an alkali-soluble indelcarboxylic acid when exposed to a small amount of water. In this way, the portion of the resist that is irradiated with light decomposes and becomes alkali-soluble and is dissolved and removed by development. This positive resist has advantages over negative resists, such as better resolution, sharper image lines, straighter image lines, and no whiskers, but it has weaker adhesion to the substrate. Since the developing solution is an alkaline solution (generally a mixture of sodium phosphate and sodium silicate), semiconductor devices are often contaminated with sodium and problems with electrical characteristics occur.

U.S. Patent No. 3,318,7573 regarding adhesion to the substrate;
It can be strengthened by treating the surface of the substrate with an organic silane binder as shown in US Pat.

This prevents the resist from peeling off during the etching process and almost solves the problem of adhesion, but the problem of sodium contamination still remains. On the other hand, developers for positive resists that do not contain alkali, such as amino alcohols, have recently been commercially available, but they have drawbacks such as poor image line definition and poor reproducibility.

The extent to which semiconductor devices are contaminated with sodium when the alkaline developer is used was investigated. In this experiment, a (311) N-type 4.4Ω Confucian silicon wafer was pre-oxidized and then subjected to an oxidation process.

Gettering the sodium here.
) A sample coated with phosphorus silicide glass and a sample not coated are prepared, and these are immersed in an alkaline developer and then washed with deionized water. Of course, do this carefully and thoroughly. Next, add a Moss capacitor to these samples. After creating (MOS●CapacitOr), a BT test was conducted.

The test results are shown in Figures 1A and B.

In other words, the same figure A is the same figure B when the phosphorsilicate glass is not coated! Experimental results when coated with 1-phosphorus silicide glass. It shows. As is clear from the figure, compared to the sample coated with phosphorus silicide glass (Figure 1 B), the sample not coated with phosphorus silicide glass (Figure 1 A) has a lower V for both +BT and -Bη wiping tests.
It can be seen that the FB shift is large and it is clearly contaminated by alkali ions. In addition, samples oxidized after being immersed in a developer exhibited large fluctuations in FB and were accompanied by deformation of the CV curve, suggesting the possibility of contamination by metal ions as well as alkali ions. Note that the above BT test refers to BT processing (Bias TemperatureTrea).
tment), NFB is the amount of surface charge,
VFB indicates flat band voltage. This invention proposes a new method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks, and is particularly a new method for developing and removing photosensitive resin in photolithography.

That is, the present invention relates to the development of a photosensitive resin using the chemical formula R.
Using an aqueous solution of trialkyl (hydroxyalkyl) ammonium hydroxide (hereinafter abbreviated as THAH) represented by 1--Syn-R4--0H]+0H- at a concentration of 1% to 8% by weight, late exposure was performed. To remove the photosensitive resin, use THAH at a concentration of more than 4% and less than 20% by weight.
Characterized by applying an aqueous solution.

In addition, in the above chemical formula, R is an alkyl group, and they do not necessarily have to have the same composition. By the way, THAH is known as a substance exhibiting alkalinity. Generally, when sodium ions are present in a silicon oxide film formed in contact with a semiconductor, the sodium ions become mobile ions, which not only significantly deteriorate the characteristics of MOS devices and planar bipolar devices, but also cause sodium ions to form on the semiconductor surface. It has been found that the presence of alkaline metal ions easily migrates to the oxide film and impairs its properties. Therefore, the reality is that such alkaline solutions are not used in semiconductor processing steps. However, as a result of various experiments, the present inventors have found that THAH aqueous solution is effective for degreasing, removing inorganic contamination, and removing extremely thin oxide films. We have confirmed that there is no significant back contamination. Next, the present inventors investigated whether the THAFI aqueous solution was applicable to developing and removing positive resists using choline [(CH3)3N(CH2CH2OH)0
Additional investigation was conducted using H].

In other words, the vertical axis shows the resist remaining film rate (film thickness after development/film thickness after coating).
A characteristic curve with the exposure amount on the horizontal axis was obtained using the concentration of the choline aqueous solution as a parameter. This is shown in Figure 2. In the same figure, curve A is 1% by weight of choline, and curve B is 4% by weight.
%, curve C shows the case where the same weight ratio is 6%, and curve D shows the case where the same weight ratio is 8%. An ideal developer is one in which the resist remaining film ratio is close to 1.0 up to a certain exposure amount, and rapidly becomes 0 when the constant exposure amount is reached. As is clear from the figure, the developer according to the present invention exhibits development characteristics similar to those of conventional alkaline developers, and it was confirmed that it can be fully used as a developer for positive resists.
Furthermore, 1% by weight of choline aqueous solution (hereinafter % indicates weight%)
It has been found that if the aqueous solution is less than 8%, the developing ability will not be sufficient, and if the aqueous solution exceeds 8%, even unexposed resist will be dissolved. In order to investigate the characteristics of a semiconductor device obtained when a choline aqueous solution is applied to such development and resist removal, the same method as that used to obtain the results shown in FIG. 1 was used. As a result, both NFB and ■FB were no different from semiconductor devices coated with a phosphosilicate glass film. This result also shows that it is an excellent processing solution. Therefore, in the present invention, it was decided to use a 1% to 8% THAH aqueous solution for developing the positive photosensitive resin, and to apply a TFIAH aqueous solution also for removing the unexposed photosensitive resin. Next, the present invention will be explained in detail with reference to Examples.

After depositing silicon oxide on an n-type silicon substrate, 1.5% of positive photosensitive resin 0FPR■ (trade name, manufactured by Tokyo Ohka Kogyo) was applied.
Deposit to μ thickness.

Next, mask alignment using a photomask is performed, but before that, a heat treatment is performed at 80° C. for about 20 minutes in order to volatilize the solvent of the photosensitive resin deposited. The mask alignment is for selecting exposed and non-exposed areas, and the exposure is performed by a light source placed parallel to the surface of the adherend. Next, the developing process begins. As the developer, choline aqueous solutions having a weight ratio of 1, 4, 6, and 8%, respectively, are used, and the sample is immersed at room temperature for 1 minute. Then wash with water for 2 minutes and dry. Then, the resist film thickness at a portion corresponding to each exposure amount is measured using a thin film measuring device. FIG. 2 is a plot of the exposure amount and resist remaining film rate obtained in this way. Curve A in the same figure
is 1% by weight of choline, curve B is 4% by weight, curve C is
shows the case where the same weight ratio is 6%, and curve D shows the case where the same weight ratio is 8%.
As shown in Figure 2, in the region to the right of curve A, that is, when the concentration of choline is less than 1%, the exposure sensitivity (
The exposure amount at the point where the curve intersects the horizontal axis) becomes worse,
It is clear that this results in an even longer exposure time required for exposure. On the other hand, focusing on the intersection of the resist residual film ratio curve and the vertical axis, the concentration of choline is 8%, that is, curve D, which is smaller than 0.5, and similarly, 6%, that is, curve C, which is 0.6. When the residual film rate is 0.5 or less,
Since the resist film thickness is less than half, there remains concern about corrosion resistance in the subsequent etching process. Therefore, the residual film ratio is preferably 0.5 or more, and the upper limit of the choline concentration is considered to be about 8%. The developing ability varies slightly depending on the type of positive resist resin, development time, solution temperature, etc., but it falls within an allowable residual film rate. In addition, in the manufacture of semiconductor devices, after the development process, heating is performed, and the undeveloped areas are inspected for marks, etc., and the exposed silicon oxide is removed by an etching process, and then washed, and then the unexposed photosensitive resin is processed. A removal washing step was performed using a 6% choline aqueous solution.

Note that the unexposed photosensitive resin is removed using a relatively high concentration of TI (A
Although it is possible to remove THAH using an aqueous solution for a long time, as a result of various experiments, it has been found that when removing unexposed photosensitive resin, it is preferable to use a THAH solution with a weight ratio of more than 4% and less than 20%. There was found. Of course, when removing the unexposed photosensitive resin, TH
It is clear that the excellent properties of the AH aqueous solution can be utilized. The photo-etching process is now completed, and the semiconductor device is completed by performing an oxidation diffusion or vapor deposition process. This example shows an example in which silicon oxide deposited on a semiconductor substrate is partially removed by photoetching, but there are also cases where mesa etching is formed on a silicon substrate and cases where interconnections are made of aluminum. Of course, it is also applicable to

Further, the method for manufacturing a semiconductor device according to the present invention includes THAH
This makes it possible to apply an aqueous solution to the development and removal of positive photosensitive resins used in photographic engraving. - According to the present invention, it is possible to achieve a residual film rate comparable to that of conventional methods, and there are no other problems. Nor. In addition, the reproducibility is better than that of conventional developing solutions that do not contain alkali, and image line sharpness is also excellent. In addition, the above TH. A
Nal, Cu, . Since the content of impurities such as Ag is extremely small, it will not remain during use in the manufacturing process, or will not migrate or be adsorbed to other members and impair the electrical characteristics of the semiconductor device. This is because THAFI can be produced from trimethylamine and ethylene oxide as shown in the following formula. Next, it is easy to produce a concentrated solution of 10% or more by the above reaction, and since a catalyst is not required and the raw materials mentioned above can be obtained with high purity, it is easy to obtain choline with good purity. There is an advantage.

Let's compare the above with one example of TFIAH (tetramethylammonium hydroxide).

The manufacturing process is as follows: R3N+RBr→R,NBrR,N
Br+AgOH. -4. Since Ag is used as in R4N+0H-+AgBr↓, Ag remains as an impurity.

Furthermore, the TMAH (7) concentration remains at a few percent. For reference, the impurity units (Ppm) of choline and TMAH were compared (see the following table). The above-mentioned high purity and high concentration are particularly important in the production of semiconductors, and the scope of application is expected to be further expanded in the future.

[Brief explanation of drawings]

In Figure 1, a Moss capacitor is formed on the sample, and Bη
This figure shows the results of the wiping test. Figure B is the one created by applying phosphorus silicide glass, Figure A is the case where phosphorus silicide glass is not applied, and the 0 mark in the figure shows the result of Ep (+BT treatment). ), × marks indicate Ep (-BT treatment), respectively.

Claims (1)

[Claims] 1. When exposing and developing a positive photosensitive resin adhered to a semiconductor, developing with an aqueous solution of trialkyl (hydroxyalkyl) ammonium or hydroxide within a concentration range of 1% to 8% by weight. A method for manufacturing a semiconductor device, characterized in that: 2. Trialkyl (hydroxyalkyl) ammonium in a concentration range of 1% to 8% by weight when removing the positive photosensitive resin adhered to the semiconductor by exposure and development;
After developing with an aqueous hydroxide solution, the unexposed photosensitive resin is converted into trialkyl (hydroxyalkyl).
A method for manufacturing a semiconductor device, characterized in that removal is performed using an ammonium hydroxide aqueous solution.